Yash Gupta, the dean of the University of Southern California’s Marshall School of Business on Thursday, resigned abruptly from his post after just 18 months.

Dr. Thomas Gilligan, vice dean for undergraduate education and a professor of finance and business economics, was named interim dean by C.L. Max Nikias, USC’s provost and senior vice president for academic affairs.

USC did not cite a reason for Gupta’s resignation. However, he was a finalist last month for the presidency of the University of Arizona, but ultimately did not get the job.

His job search came after a precipitous drop by Marshall in the influential U.S. News & World Report ranking of top U.S. business schools. Three months after Gupta took the post in July 2004, the Marshall School dropped 10 places. Last year, it fell further down the rankings to No. 27; it was No. 17 in 2002.

“Dr. Gupta has informed me that his career path has brought him to the conclusion that he should resign from his position,” Nikias said in a memo to faculty members.

Gupta, a professor of operations management, was recruited by USC from the University of Washington’s Business School, where he helped raise $50 million for the school and doubled enrollment in its MBA programs. Previously, Gupta served as a dean and professor at the University of Colorado at Denver.