MICHAEL Appleton's solitary game as caretaker boss ended in agony as Albion surrendered a three-goal lead in this incredible basement battle.
The first-half couldn't have gone any better for 'Appy', who will hand the reins to new head coach Roy Hodgson on Monday, as strikes from Graham Dorrans and Jerome Thomas inside the opening eight minutes, plus a Winston Reid own goal, gave the hosts a 3-0 lead.
But in a real game of two halves, West Ham set up a thriller of a second period when strike duo Demba Ba and Carlton Cole netted in the 50th and 58th minutes respectively.
There were further chances at both ends before the Baggies' resistance was finally broken a third time when Ba made it 3-3 with five minutes left.
Albion could draw consolation from the fact they didn't lose the game, thus keeping the Hammers two points behind them, and that Hodgson now knows the kind of task facing him, after witnessing the best and worst his new team have to offer.
Appleton made two changes from the Eastlands defeat, with fit-again Dorrans and Gonzalo Jara coming in for James Morrison and the injured Steven Reid.
There was also a new system, with Marc-Antoine Fortuné and Peter Odemwingie paired up front in a 4-4-2 formation.
Avram Grant made four changes from their reverse at home to Blues as Cole, Luis Boa Morte, Manuel Da Costa and Ba replaced Victor Obinna, Robbie Keane, Matthew Upson and Freddie Piquionne.
The two teams started the day separated by only two points as 17th entertained 20th in this crucial fixture at the foot of the table.
Hodgson had opted for a low profile at the game so that there were no distraction for Appleton and the team.
But he was still afforded a warm reception from the home fans when he took his seat next to sporting & technical director Dan Ashworth just before kick-off.
Albion were positive from the first whistle and a long spell of keep-ball created a shooting opportunity for Fortuné, who fired straight at Robert Green from 20 yards.
And it got even better in the third minute.
Odemwingie shrugged off Mark Noble before teeing up Dorrans - a transfer target for West Ham in the summer - who took one touch before blasting an unstoppable 25-yard shot past Green - his first-ever Premier League goal.
It was almost 2-0 just two minutes later when Green's parry from Odemwingie's 15-yard drive fell invitingly for Chris Brunt. The skipper would have been celebrating a goal had Fortuné not unwittingly blocked his effort two yards out.
But Albion DID score again in the eighth minute.
The hard-working Fortuné laid the ball back for Thomas who expertly curled a shot into the far bottom corner from 15 yards.
The Baggies were absolutely flying and Thomas looked certain to score when he outmuscled Da Costa to latch onto Brunt's aerial ball and rounded Green. But he lost his balance just as he shaped to slot into an empty net, allowing Da Costa to clear.
Albion suffered an injury blow on 14 when Youssouf Mulumbu hobbled off and was replaced by Morrison.
But it was still all Albion and, on 18, Odemwingie will feel he should have done much better with a free header from Dorrans' corner, which he directed tamely at Green from six yards.
The Hammers did not record their first shot at goal until the 20th minute when January singing Ba blazed well wide from 20 yards, with his effort curling out for a throw-in on the far touchline.
Striker partner Cole was also well off target from similar distance two minutes later.
Boaz Myhill finally had a save to make on 29 when he comfortably pushed away a long-range Gary O'Neil effort which had skipped up awkwardly off the turf.
Albion had strong penalty appeals turned away two minutes later when Brunt's hanging free-kick clearly struck Reid's arm in the box - but referee Lee Mason said no spot-kick.
But the Baggies felt justice was done inside a minute when Reid handled Dorrans' free-kick into his own net to make it 3-0.
West Ham finally came to life during the closing stages of the half.
Jara had to make a last-ditch challenge on Scott Parker to prevent the England international having a clear run at goal.
And the East Londoners went agonisingly close when Myhill pulled off a wonder save by pushing Ba's low drive onto his post after the Senegal striker had exchanged a neat one-two with Cole. Morrison hacked the loose ball clear.
Albion surged back up the other end and Green brilliantly kept out Dorrans' long-range missile with his finger-tips.
Thomas then showed terrific control before firing just wide from 20 yards.
But in the third minute of stoppage time, Grant's men hit the woodwork again when O'Neil smashed the bar with a dipping 25-yarder. Scharner denied Luis Boa Morte a certain goal by diverting his effort over from the rebound.
From Noble's ensuing corner, Da Costa headed straight into Myhill's grateful arms.
There was more penalty woe for Albion at the start of the second half when Fortuné went down under Reid's challenge in the box - but referee Mason waved play on.
But West Ham had begun the second period with far more purpose and they pulled a goal back on 50.
Paul Scharner misjudged the flight of Noble's diagonal ball into the box which Ba controlled before blasting past Myhill.
West Ham piled forward again and Myhill showed a safe pair of hands to hold onto Boa Morte's flick header from Noble's corner.
It was game on in the 58th minute when the visitors made it 3-2.
Sub Piquionne was left totally unmarked at the far post to head Noble's free-kick into the danger-zone which Cole nodded home.
On the hour-mark, it was almost 3-3 when Piquionne out-jumped Jonas Olsson and saw his header from Wayne Bridge's cross loop onto the bar and out for a goal kick.
Albion regrouped and a terrific move involving Dorrans and sub Giles Barnes resulted in Odemwingie seeing an 18-yard effort pushed wide by Green.
Back came the Hammers and Nicky Shorey kept the scoreline as it was by blocking Ba's effort on the goalline from Noble's pull-back.
The action swung straight to the other end and Green gobbled up Morrison's 25-yard drive at the second attempt.
It was real edge of the seat stuff and Albion were relieved to see Ba fire into the side-netting from O'Neil's lay-off.
Moments later, Morrison was off target with a long-range effort.
But Albion just couldn't hold on and after they fell asleep at a short corner in the 85th minute, Ba volleyed home at the far post from Noble's centre.
Incredibly, Albion could still have won it.
On 89, Shorey and Morrison combined to tee up Odemwingie, who could only side-foot tamely at Green from an acute angle.
Then, two minutes into stoppage time, Odemwingie drifted inside from Shorey's pass, beating both Bridge and Reid, before firing wastefully at Green.
But Albion could also have lost it.
On 93, Da Costa headed just over from Noble's corner while, with virtually the last kick of the game, Piquionne missed the target with a 18-yard rocket.
ALBION (4-4-2): Myhill; Jara, Scharner, Olsson, Shorey; Brunt, Mulumbu (Morrison 14), Dorrans (Tamas 83), Thomas (Barnes 61); Fortuné, Odemwingie. Subs not used: Carson (gk), Ibanez, Vela, Cox.
WEST HAM (4-4-2): Green; Jacobsen, Reid, Da Costa, Bridge; O'Neil (Spector 78), Parker, Noble, Boa Morte (Piquionne 57); Cole, Ba. Subs not used: Boffin (gk), Hitzlsperger, Kovac, Faubert, Hines.
GOALS: ALBION - Dorrans (3), Thomas (8), Reid (own goal 32). WEST HAM - (Ba 50 & 85), Cole (58).
BOOKINGS: ALBION - Dorrans (unsporting behaviour 29), Brunt (foul 57). WEST HAM - Boa Morte (foul 30), Noble (foul 39), Spector (foul 88).
REFEREE: L Mason (Bolton).
ALBION STARMAN: Graham Dorrans.
PIC: GREAT START...Dorrans celebrates his opener