Mark Harmon stars as Leroy Jethro Gibbs on NCIS.
While he considered "advertising or law" as careers after college, Harmon became an actor and has spent much of his career portraying law enforcement and medical personnel.
After several years of supporting guest roles on episodic TV shows such as Police Woman, Laverne & Shirley and The Hardy Boys/Nancy Drew Mysteries, Harmon landed his first prominent role in the 1980 primetime soap opera Flamingo Road.
The series was short-lived, but he soon landed the role of Dr. Robert Caldwell on the prestigious NBC Emmy-winning series St. Elsewhere in 1983.
In 1986, Harmon left the series as his character contracted HIV through unprotected heterosexual intercourse - a storyline that was notable for being one of the first instances where a major recurring character contracted the virus.
Harmon's next regular television role would be as Chicago police detective Dickie Cobb for two seasons (1991-1993) on the NBC series Reasonable Doubts.
He returned to ensemble medical shows on the series Chicago Hope, in which he played Dr. Jack McNeil from 1996-2000. In May 2002, he had a guest role as Secret Service Special Agent Simon Donovan on The West Wing.
Harmon took a lead role in two episodes of JAG in April 2003, which introduced viewers to him in the role of NCIS agent Gibbs.
Harmon has been married to actress Pam Dawber since 1987. The couple have two sons: Sean Thomas Harmon (born 1988) and Ty Christian Harmon (born 1992).