Cline resigned his position after financial mismanagement was discovered within the Oklahoma State Department of Health.
Cline also served as the Chairman of the Governing Board for a Harvard Community Teaching Hospital in Cambridge for several years.
As Commissioner, Cline was responsible for providing public health services relating to mental illness and substance abuse.
President George W. Bush nominated Cline to serve as the Administrator of the Substance Abuse and Mental Health Services Administration, an agency of the United States Department of Health and Human Services, in November 2006, and his nomination was confirmed by the U.S. Senate in December.
At the end of August 2008, Terry Cline became the HHS Department's Health Attaché and representative at the U.S. Embassy in Baghdad, Iraq.
Cline's resignation was prompted by allegations of financial mismanagement within the Department, which were subsequently investigated by the Oklahoma State Auditor.