Ben Gazzara as Al Capone

Harry Guardino as Johnny Torrio

Sylvester Stallone as Frank Nitti

Susan Blakely as Iris Crawford

John Cassavetes as Frankie Yale

Frank Campanella as Big Jim Colosimo

John Orchard as Dion O'Banion

Carmen Argenziano as Jack McGurn

George Chandler as Robert E. Crowe

John Davis Chandler as Hymie Weiss

Royal Dano as Anton J. Cermak

Joe De Nicola as Charles Fischetti

Angelo Grisanti as Angelo Genna

Peter Maloney as Jake Guzik

Dick Miller as Joe Pryor

Robert Phillips as Bugs Moran

Martin Kove as Pete Gusenberg

Mario Gallo as Giuseppe Aiello

George Milan as William H. Thompson

Russ Marin as Joseph Stenson

Tony Giorgio as Antonio Lombardo

John Martino as Tony Amatto

Bert Conway as Frank Loesch

Don Pulford as William Cooper

Pamela Toll as Mrs. Atkins

Eugenia Stewart as Miss Detwiller

Don McGovern as N.Y. Cop #1

Redmond Gleeson as N.Y. Cop #2

John Finnegan as N.Y. Police Lt.

Laurence Hagen as Samuel Ettelson

Tom Cook as Sam Volenta

Vincent Barbi as Solly

Tina Scala as Mrs. Torrio

James V. Christy as Thomas Bronk

Jack Ackerman as Adam Heyer

Ralph James as Judge J.H. Wilkerson

Carmen Filpi as Waiter

Jim Galante as John May

John Howard as Warden J. Johnston

Beach Dickerson as Joe Kepka

John C. Broderick as Maitre d'

Chuck Traynor as Senator

James R. Sweeney as Prison Doctor

George Engelson as Torrio's Doctor

Deborah Klose as Female Reporter

John Favorite as First Reporter

John Armond as Second Reporter

Jack O'Leary as Pool Hall Owner

Ben Marino as Frank Gusenberg

Vincent Di Paolo as Mob Soldier (uncredited)