Dr. Mark Sloan has been in medicine for over 40 years and is chief of internal medicine at Community General Hospital as well as being a consultant to the LAPD. As a doctor, he the black sheep of the family as he comes from "a long line of cops". His son Steve, with whom Mark shares his Malibu beach house, is continuing that tradition. Mark also has an estranged daughter, Carol, a nurse, who lives in Northern California. His is a widow, since his wife Katherine died of cancer a little over 10 years ago. He has an older sister, Dora, who owns a travel agency, and has a younger brother, Stacey, who owns a malt shop in Arkansas and has a tendency to sleepwalk.

Mark likes jazz and Glenn Miller, enjoys dancing (soft shoe and tap), can play a number of instruments including the clarinet and keyboards, is good at chess, can often be found rollerblading when his car breaks down and his party piece is magic tricks.