CORVALLIS - Sophomore Tina Andreana's one-hitter led Oregon State to a 3-1 upset of No. 5 Arizona on Friday.
Andreana (4-4) gave up eight hits and struck out seven Wildcats in the series opener at the OSU Softball Complex.
The series concludes at noon Saturday with a doubleheader.
OSU improved to 1-3 in the Pac-10 and 17-11 overall, while Arizona fell to 3-1, 32-7.
Andreana got out of bases-loaded jams in the second (with a third-out foulout) and fourth (with an inning-ending strikeout).
OSU scored in the third on Desiree Beltran's two-run single and added a run in the fourth on a bases-loaded single by Erin Guzy. The scoring came off Kenzie Fowler (20-5), the reigning national player of the week.
UA's run came in the seventh, when Brigette Del Ponte led off with a home run.