Ruffalo had minor roles in films including The Dentist (1996), the low-key crime comedy Safe Men (1998) and Ang Lee's Civil War Western Ride with the Devil (1999). Through a chance meeting with writer Kenneth Lonergan, he began collaborating with Lonergan and appeared in several of his plays, including the original cast of This is Our Youth (1996), which led to Ruffalo's role as Laura Linney's character's brother in Lonergan's Academy Award-nominated 2000 film You Can Count On Me. He received favorable reviews for his performance in this film, often earning comparisons to the young Marlon Brando, and won awards from the Los Angeles Film Critics Association and Montreal World Film Festival. His next role was in 2001 in Rod Lurie's The Last Castle playing a bookie in a military prison alongside Robert Redford. This led to other significant roles, including the films XX/XY (2002), Isabel Coixet's My Life Without Me (2003), Jane Campion's In the Cut (2003), Michel Gondry's Eternal Sunshine of the Spotless Mind (2004), and We Don't Live Here Anymore (2004), which is based on two short stories written by Andre Dubus. He appeared opposite Tom Cruise as a narcotics detective in Michael Mann's crime thriller Collateral (2004).