Robert De Niro
Leonard Lowe
Robin Williams
Malcolm Sayer
Julie Kavner
Eleanor Costello
Max von Sydow
Peter Ingham
Alice Drummond
Lucy Fishman
Bradley Whitford
Dr. Tyler
John Christopher Jones
Dr. Sullivan
Mary Catherine Wright
Nurse Beth
Harvey Miller
Hospital Director
Tanya Berezin
Psychiatrist
Peter Stormare
Neurochemist
Waheedah Ahmad
Hysterical Woman
Christina Huertes
Christina
Judy Jacksina
Hospital Receptionist
Chris Carolan
EEG Technician
Debra Kovner-Zaks
Cafeteria Nurse
Max Rabinowitz
Ward #5 Orderly
Gordon Joseph Weiss
Ward #5 Patient
Byron Utley
Ward #5 Patient #2
Anthony McGowen
Ward #5 Patient #3
Paul Montgomery
Ward #5 Patient #4
Leonard Tepper
Ward #5 Patient #5
Vincent Pastore
Ward #5 Patient #6
Howard Feller
Ward #5 Patient #7
Tomislav Novakovic
Bartender
Anthony J. Nici
Young Leonard
Oliver Block
Leonard's Friend #1
Buck Smith
Leonard's Friend #2
Harry L. Seddon
Medical Student
Jack Mulcahy
Psych Ward Intern
Jason W. Fuchs
Pot-Head Hippie
Vin Diesel
Hospital Orderly (uncredited)