Julie Christie as Susan Harris

Fritz Weaver as Alex Harris

Gerrit Graham as Walter Gabler

Berry Kroeger as Petrosian

Lisa Lu as Soong Yen

Larry J. Blake as Cameron

John O'Leary as Royce

Alfred Dennis as Mokri

Davis Roberts as Warner

Patricia Wilson as Mrs. Talbert

Dana Laurita as Amy

Michelle Stacy as Marlene

Felix Silla as Baby

Tiffany Potter as Baby

E. Hampton Beagle as Night Operator

Michael Glass as Technician

Barbara O. Jones as Technician

Monica MacLean as Joan Kemp

Peter Elbling as Scientist

Georgie Paul as Housekeeper

Robert Vaughn as Proteus IV (voice) (uncredited)