This tall, curly-haired son of former Major League Baseball commissioner A Bartlett Giamatti and older brother of actor Paul Giamatti, began his career with a one-shot appearance in a TV commercial at age nine. After training at Yale, Marcus Giamatti embarked on a stage career that included work in regional theaters before he landing a role in a 1989 Lincoln Center staging of "Measure for Measure". The following year, he broke into features in "Mr. and Mrs. Bridge" and followed with roles in the formulaic gridiron comedy "Necessary Roughness", starring Scott Bakula, and the CBS movie "Aftermath: A Test of Love" (both 1991), as well as guesting that year on NBC's "Hunter". A 1992 episode of "Quantum Leap" reunited him with Bakula, and he finally achieved a more prominent profile as Corey Parker's slick, unctuous office mate in the Fox sitcom "Flying Blind" (1992-93). Between film and movie assignments, Giamatti returned to the stage, co-starring with his brother in Michael Cristofer's 1996 two-character Off-Broadway play "The Blues Are Running". He was featured the next year in Horton Foote's Pulitzer-winning "The Young Man From Atlanta" alongside heavyweights Rip Torn and Shirley Knight. Though he continued to land small roles in features (i.e., Barry Levinson's "Jimmy Hollywood" 1994) and TV-movies (e.g., TNT's critically-acclaimed "Pirates of Silicon Valley" 1999), Giamatti's next great opportunity came as a series regular again in "Judging Amy" (CBS, 1999- ), playing Amy Brenneman's uptight brother Peter Gray. He also portrayed Guildenstern in a cable version of "Hamlet" (Odyssey, 2000), directed by and starring Campbell Scott.