Limited series I KNOW THIS MUCH IS TRUE debuts April 27

Limited Series I KNOW THIS MUCH IS TRUE, Starring Mark Ruffalo; Written For Television And Directed By Derek Cianfrance, Debuts April 27, Exclusively On HBO

Based On Wally Lamb's Award-Winning New York Times Bestseller Of The Same Name

Executive Produced By Derek Cianfrance, Ben Browning, Glen Basner, Mark Ruffalo, Gregg Fienberg, Lynette Howell Taylor, Wally Lamb And Anya Epstein; Jamie Patricof Co-Executive Produces

From acclaimed writer and director Derek Cianfrance ("Blue Valentine," "The Place Beyond the Pines") comes I KNOW THIS MUCH IS TRUE, a six-part limited drama series debuting this April, starring Mark Ruffalo (Emmy(R) winner for HBO's "The Normal Heart"), who also serves as an executive producer, as identical twin brothers Dominick and Thomas Birdsey in a family saga that follows their parallel lives in an epic story of betrayal, sacrifice and forgiveness. The series, set in the fictional town of Three Rivers, Connecticut, shows Dominick and Thomas at different stages in their lives, beginning in their present in the early 1990s with both brothers approaching middle-age, filled in with Dominick's flashbacks to their young adulthood and childhood.

The limited series will also be available on HBO NOW, HBO GO, HBO On Demand and partners' streaming platforms.

Melissa Leo (Emmy(R) nominee for HBO's "All the Way" and "Mildred Pierce," Academy Award winner for "The Fighter,") stars as Ma (ConcettinaIpolita Tempesta Birdsey), mother of Dominick and Thomas; Emmy(R) winner Rosie O'Donnell as Lisa Sheffer, a social worker for unit two at the Hatch Forensic Institute; Emmy(R) winner Archie Panjabi as Dr. Patel, Thomas' newly appointed psychologist; Imogen Poots as Joy Hanks, Dominick's live-in girlfriend; John Procaccino as Ray Birdsey, Dominick and Thomas' stepfather; Rob Huebel as Leo, Dominick's best friend; Philip Ettinger as the young adult Dominick and Thomas Birdsey; Aisling Franciosi as young Dessa Constantine; Michael Greyeyes (HBO's "True Detective") as Ralph Drinkwater, a former classmate from Dominick and Thomas' youth whose life intersects once again with Dominick; Guillermo Diaz as Sergeant Mercado; Marcello Fonte as Domenico Onofrio Tempesta, Dominick and Thomas' maternal grandfather from Sicily; Bruce Greenwood as Dr. Hume, head of the board at the Hatch Forensic Institute; Brian Goodman as Al, an older cop; with Academy Award nominee Juliette Lewis as Nedra Frank, a self-absorbed grad student hired by Dominick; and Emmy(R) nominee Kathryn Hahn as Dessa Constantine, Dominick's ex-wife.

The limited series is written for television and directed by Derek Cianfrance. Cianfrance executive produces along with Ben Browning & Glen Basnerfor FilmNation Entertainment, Mark Ruffalo for Willi Hill Productions, Gregg Fienberg, Lynette Howell Taylor, Wally Lamb, Anya Epstein; Jamie Patricof co-executive produces.