On Assignment, Inc. said Monday that its Chief Financial Officer, Michael Holtzman, resigned from his position on Dec.8 due to medical reasons.

Holtzman has been on a medical leave of absence from the Calabasas-based staffing firm since Oct. 30 and decided to submit his resignation to focus on his recovery, the company said. On Assignment said that a search for Holtzman’s replacement will commence immediately.

Holtzman joined the company in May 2002 and has served as the company’s CFO since early 2005. Specifics of Holtzman’s resignation were not given.

Shares in On Assignment were flat at $11.02.