Indiana is No. 1 in the Associated Press' Top 25 for the fourth straight week, and Gonzaga moved to No. 2 for the first time in school history.
The Bulldogs were third last week, matching their previous best ranking.
"The polls mean a lot more this time of year than they do in November, December, even January," coach Mark Few said. "All of us are being judged on the true body of work. It's definitely rewarding.
"It establishes us as a national program, which I believe we have been for the last 10 years. This group has done a great job of competing at that level, winning games at the highest level."
No. 5 Miami dropped from second after losing to Wake Forest. Florida fell from No. 5 to No. 8. Saint Louis moved in at No. 18, and Colorado State and VCU dropped out.
Louisiana Tech moved in for the first time since a 13-week run in 1984-85, it only other appearance. Those Bulldogs, who are 25th, were led then to a ranking as high as No. 7 by forward Karl Malone.