Martin Scorsese	...	(Director)
William Monahan, Siu Fai Mak	...	(Writer)
Leonardo DiCaprio	...	William M. 'Billy' Costigan
Matt Damon	...	Det. SSgt. Colin Sullivan
Jack Nicholson	...	Francis 'Frank' Costello
Mark Wahlberg	...	Det. SSgt. Dignam
Martin Sheen	...	Det. Capt. Oliver Queenan
Ray Winstone	...	Mr. French
Vera Farmiga	...	Dr. Madolyn Madden
Anthony Anderson	...	Officer Brown
Alec Baldwin	...	Det. Capt. George Ellerby
Kevin Corrigan	...	Cousin Sean
James Badge Dale	...	Officer Barrigan
David O'Hara	...	Fitzy
Mark Rolston	...	Timothy Delahunt
Robert Wahlberg	...	Agent Frank Lazio - FBI
Kristen Dalton	...	Gwen
Michael Ballhaus	...	Cinematographer

Comments: Better than Infernal Affairs if you ask me. Jack

Summary: Two just-graduated officers from Massachusetts State Police Academy follow opposite sides of the law: William Costigan is assigned to work undercover with the Irish mobster Frank Costello to get evidences to arrest him. His true identity is only known by his superiors Dignam and Oliver Queenan. The protégée of Costello, Colin Sullivan, is promoted in the Massachusetts State Police and is the informer of Costello. Each police officer gives his best effort trying to disclose the identity of the other "rat".