Senior center Kaitlin Langer scored eight of her 19 points in a key 13-3 fourth-quarter run and the No. 2-ranked Tommies (29-0) held off the University of Chicago Maroons (19-8), 73-69, in Saturday's second-round NCAA Division III women's basketball playoff action in Schoenecker Arena.
The Toms sank 26-of-32 free throws -- 12-of-14 in the final quarter -- to just 11-of-20 for the Maroons.
They advance to the NCAA Sweet 16 round for the fifth time in the last six seasons and improve to 27-5 overall in the postseason (MIAC and NCAA) since the 2011-12 season.
The lively game had six ties and 17 lead changes.
Langer added 10 rebounds for her 26th career double double. Sophomore guard Lucia Renikoff scored a career-high 17 points, and Maddie Wolkow had 13 points and three steals.
Chicago shot 49 percent from the floor and had two players record double doubles, but it wasn't enough. Britta Nordstrom had 18 points and 12 rebounds, and Olariche Obi added 10 points and 10 rebounds
Wolkow's buzzer-beater trey capped an 11-3 run and pulled St. Thomas even at 34-34 at halftime.
UST, which helped force 18 Chicago turnovers, rallied from another eight-point deficit, this time early in the third quarter.
The Maroons' last lead was at 52-51 on Nordstrom's layup with 7:40 to play. But St. Thomas used a 13-3 run over the next 5:48 to lead by nine.