Nicky Forster bagged two goals for Reading as Neil Warnock's high-flying FA Cup quarter-finalists were brought down to earth with a bump.
Sheffield United, still harbouring dreams of automatic promotion, tumbled to their third successive league defeat after Michael Brown handed them a dream start.
The scoreline could have been even more embarrassing for the Bramall Lane but for three spectacular saves from Paddy Kenny.
Brown struck a spectacular goal from 25 yards with just four minutes gone, curling his free-kick into the top left hand corner after Dean Windass had been brought down, for his 12th goal of the season.
The impressive Brown picked out Stuart McCall minutes later with a pass inside and the veteran midfielder finished with a stinging drive from outside the area, tipped round the foot of the post by Marcus Hahnemann.
Reading were back on level terms in the 35th minute after sloppy defending by the home side. Andy Hughes had time to slip in a shot, blocked by centre-back Robert Page and Forster steamed in to steer the loose ball past the advancing Kenny from 14 yards.
Brown squandered a chance working his way into the area before firing over the bar from 16 yards. Minutes later Forster almost snatched the lead with a fierce strike from 25 yards that was smothered at the near post by Kenny.
Substitute Nathan Tyson went even closer cutting in from the left to lash in a strike from the edge of the area, but again Kenny was in the way producing an eye-catching stop to push the ball away.
Hughes had a long-range effort turned over the bar by the United keeper before Reading snatched a second in the 74th minute. Kenny could only push away Hughes' shot and Adie Williams finished off from close range.
Reading killed off United nine minutes from time, Tyson's fiercely driven cross was turned in by Forster from the tightest of angles.