Gregory Peck as David Stillwell

Diane Baker as Shela

Walter Matthau as Ted Caselle

Robert H. Harris as Dr. Broden

Kevin McCarthy as Sylvester Josephson

Leif Erickson as The Major

Walter Abel as Charles Stewart Calvin

George Kennedy as Willard

Jack Weston as Lester

Anne Seymour as Frances Calvin

House Jameson as Bo

Hari Rhodes as Lt. Franken

Syl Lamont as Benny

Eileen Baral as Irene

Neil Fitzgerald as Joe Turtle

Franklin Cover as Group Leader

Don Anderson as

Bill Baldwin as

Al Beaudine as

Roxane Berard as

Robert Brubaker as

Toni Covington as

John Crowther as

Robert Dahdah as

Ann Doran as Tenant in Apartment 3R (uncredited)

Jerry Dunphy as

Douglas Evans as

Harry Fleer as

Rian Garrick as

Gerald Gordon as

Damian O'Flynn as Bar Patron (uncredited)

John Pedrini as

Barbara Perry as Office worker (uncredited)

Murray Pollack as Detective (uncredited)

Bill Quinn as Eddie - Bartender (uncredited)

Allan Ray as

Walter Reed as Reporter (uncredited)

Victor Romito as

George Simmons as

Ann Staunton as

Bert Stevens as

Robert Swan as Police Sergeant (uncredited)

Aline Towne as Dr. Broden's Receptionist (uncredited)

Howard Wendell as

Myron Healey as Bar Patron Discussing Watermelon (voice) (uncredited)