Dr. Cox is an attending physician and residency director at Sacred Heart Hospital. He's the sarcastic, bitter mentor of J.D. Dorian " a role he clearly relishes. Cox believes his rough treatment of J.D. is good conditioning for the challenges of hospital life. He has a slew of negative nicknames for his hospital staffers; however, he deftly avoids teasing Nurse Carla Espinosa.

Dr. Cox also has a bit of a drinking problem and this becomes more of an issue when situations arise at the hospital. He has a complex relationship with his ex-wife Jordan, with whom he has two children. Despite their history, the two maintain a somewhat functional relationship.

He frequently clashes with hospital chief Dr. Bob Kelso, whom he occasionally refers to as "The Devil". After Kelso retires Dr. Cox becomes chief.