The Badgers improved to 16-0 (3-0 Big Ten), the best start in school history.
Wisconsin shot 53 percent from the field in the first half to open up a 25-point lead by halftime. The Illini (13-3, 2-1) stumbled badly in their debut this year as a Top 25 team and lost a sixth straight to their border rival.
Rayvonte Rice led Illinois with 19 points on 7-of-21 shooting.
The Illini missed 13 straight shots, some on easy looks, while Wisconsin methodically wore them down inside and on the perimeter during the big first-half run.
The balanced Badgers had five players with at least 11 points, with Frank Kaminsky adding 15 and freshman Nigel Hayes 11 off the bench. Traevon Jackson had 15 points and went 7 of 7 from the foul line.
The end of Wisconsin's first-half run typified Illinois' frustrating evening. Kaminsky, Wisconsin's 7-foot outside shooter, hit a 3 to make it 29-10 with about 10 minutes left before proving his worth at the other end.
The only defender back initially against two Illini, Kaminsky got in A
brams' way to force a missed jumper. Illinois grabbed the rebound, but Egwu missed a short layup.
Two more offensive rebounds, two more misses before the ball went out of bounds to Wisconsin.
By contrast, the Badgers played with typical efficiency at the other end, a hallmark for coach Bo Ryan's teams.
The ball wound around the perimeter before going into Dekker. The lithe 6-foot-7 forward backed down his defender with about 5 seconds left on the shot clock before turning and hitting an easy layup.
Bertrand's short jumper finally ended the run, but Illinois was well out of it already by then, down 33-12 with 7:56 left in the first half. The Badgers gave them a few easy looks on the defensive end but Illinois failed to convert.
Illinois outrebounded Wisconsin 48-35, including 25-5 on the offensive end, but still lost badly.
Coach John Groce's team played a little better to open the second half and still could get no closer than 17.
Just another solid win for Wisconsin. The Badgers aren't necessarily flashy, but they've got much more firepower offensively than in years past.
Dekker can beat opponents off the dribble, as he did on a pretty diagonal drive through the lane that ended with a hesitation move and three-point play during the start of the 20-0 run.
Kaminsky can hit the 3 or smoothly maneuver in the post. The pesky Brust can make opponents pay from the perimeter, finishing 4 of 8 from 3-point territory.
And what's more, Wisconsin takes care of the ball. The NCAA leader with just 8.47 turnovers per game had just four on Wednesday, including two for Jackson after the point guard had a career-high seven his previous outing against Iowa.
Illinois gets three days to regroup before heading back on the road for the short trip Sunday to Northwestern. It has been 25 years since Illinois beat a Top 5 team on the road, a 70-67 win at No. 3 Indiana.