Dean of the Faculty of Arts and Sciences (FAS) Jeremy R. Knowles will step down at the end of the academic year.

Knowles, who is the Houghton professor of chemistry and biochemistry, said he will return to teaching.

Knowles notified the Faculty of his decision this morning through a letter broadcast to professors via e-mail.

“Now, after 11 very rewarding (if sometimes too abundantly busy) years, I have decided to return to the Faculty,” Knowles said in a statement released yesterday. “I do so with a sense of pride in what we as a Faculty have aspired to achieve together, and with a cheerful confidence in Harvard’s capacity to grow ever stronger.”

Knowles arrived at Harvard from Oxford in 1974, and took the helm of the Faculty in July 1991, as former University President Neil L. Rudenstine was taking over the reigns of the University.

He was the first scientist to serve as Dean of FAS.

During his tenure, Knowles has led the Faculty through a number of major initiatives in curricular reform, physical planning, and fundraising.

While sudden, Knowles’ decision was not unexpected.

Many faculty and administrators say they expected Knowles to step down in the near future—although some were caught off guard by Knowles announcement this morning. After a decade in office, Knowles told The Crimson last year that when he started the job in 1991 he had planned to serve roughly ten years.

“I think many of us expected he would stay on through the presidential transition to make sure there was continuity and at some point he’d seek to pass the baton,” Dean of the Graduate School of Arts and Sciences Peter T. Ellison said.

University President Lawrence H. Summers will chose Knowles’ successor. The Dean of FAS has traditionally been an internal appointment.

—Staff writer Kate L. Rakoczy can be reached at rakoczy@fas.harvard.edu.