Darren Bent's second-half goal gave Ipswich a slender advantage in their play-off semi-final against West Ham.
Bent headed home after Richard Naylor's powerful right-foot strike bounced back off the crossbar and bounced up invitingly off Tomas Repka.
Ipswich's Ian Westlake came close in the first half, but his shot was cleared off the line by Andy Melville.
Bobby Zamora twice shot just wide for the Hammers, and Michael Carrick saw a free-kick well saved by Kelvin Davis.
But Ipswich probably did enough to justify the win which leaves the Hammers needing a strong comeback in the second leg on Tuesday.
The main surprise in a frantic opening half was that neither side found the net.
28 mins: Melville clears off line for Hammers
57 mins: Bent heads home after Naylor hits bar
79 mins: Davis saves Carrick's free-kick
Westlake had the first clear chance after seven minutes, but his right-foot drive flew one yard wide.
Marlon Harewood had the ball in the net for the Hammers on 11 minutes, but was penalised for an unnecessary foul on John McGreal.
The frantic pace continued, with Harewood firing into the side netting, before Ipswich's Jim Magilton saw a low drive deflected just wide by Melville with Stephen Bywater beaten.
Bywater also had to be alert on 20 minutes after Matt Richards' low cross deflected wickedly off Repka.
Bobby Zamora fired a warning after a quick West Ham break, his shot zipping narrowly wide.
West Ham needed a spectacular goal-line clearance from Melville on 28 minutes who booted Westlake's shot clear with Bywater woefully out of position.
Shortly afterwards, Naylor also came close for Town, beating the Hammers' offside trap but mis-hitting the ball from three yards and seeing it trickle agonisingly wide.
In between Zamora had time to cleverly fashion a chance, only to fire a wicked shot across the face of goal.
The tempo slowed towards half-time, but Jermaine Wright came within inches of giving Town the lead with the last kick of the half, hitting Magilton's corner full on the volley only to see it hit the side netting.
The second half began at the same high-tempo pace of the first, with Harewood heading a corner inches over.
But it was the home team who were celebrating as Bent put them in front on 57 minutes capitalising on Naylor's great shot off the bar.
The Hammers seemed shaken up by the strike and struggled to find the cutting edge which had characterised their early play.
But Michael Carrick came close with a 79th-minute free-kick which Kelvin Davis saved well, and substitute Joel McAnuff saw a follow-up shot blocked.
But Ipswich otherwise held out comfortably to ensure a slender advantage for the second leg.
Ipswich: Davis, Wilnis, McGreal (Kuqi 83), Elliott, Richards, Wright, Magilton (Bart-Williams 76), Miller, Westlake, Bent (Bowditch 69), Naylor. Subs not used: Price, Reuser.
Booked: Magilton, Wilnis.
West Ham: Bywater, Repka, Melville, Dailly, Mullins, Harewood (Deane 78), Lomas, Carrick, Etherington (Reo-Coker 90), Zamora (McAnuff 69), Connolly. Subs not used: Srnicek, Ferdinand.
Referee: M Clattenburg (Co Durham).