Cambridge took a step closer to automatic promotion from League Two with a 4-2 away win at Leyton Orient thanks to two goals from Joe Ironside.
Shilow Tracey and Paul Mullin were also on target while the Os replied through Dan Kemp and a Declan Drysdale own goal.
Ironside put Cambridge in front on 19 minutes when he stabbed home a Jack Iredale cross but the home side levelled in the first minute of first-half added time when Kemp fired a shot into the top corner.
The Us restored their lead on 64 minutes when Tracey headed home from six yards and five minutes later, Mullin notched his 29th league goal of the campaign from the penalty spot following a foul by Jamie Turley on Greg Taylor.
Orient reduced the deficit on 72 minutes after Conor Wilkinson headed against the woodwork and the ball bounced off Drysdale into the net.
But Ironside restored the two-goal cushion from close range on 80 minutes with his 14th league goal of the season.