Brian Dennehy as John Wayne Gacy

Michael Riley as Joe 'Polock' Kozenczak

Margot Kidder as Rachel Grayson

Meg Foster as Linda Carlson

Martin Julien as Ted Koslo

Scott Hylands as Mike Paxton

John Boylan as Atkins

David Eisner as Williams

Tony De Santis as DeMarco

Mark Humphrey as King

Gary Reineke as Petrie

Tim Progosh as Morris

Danny Pawlick as Santori

Bruce Ramsay as Bragg

Brenda Bazinet as Alice Pearson

Liliane Clune as Marcia Kozenczak

Toby Proctor as Michael Kozenczak

Christopher Marren as Billy

Gerry Quigley as Walden

Nicholas Pasco as Barton

Michael Copeman as Chief Cameron

James Kee as Hoskins

Brigette Lawson as Pam

Jay Brazeau as Jake Burns

Cynthia Preston as Cindy Beck

Andrew Gillies as Vincent Austin

Kurt Reis as Waldron

Judith Goodwin as Mrs. Gant

Shawn Lawrence as Mr. Gant

Jacqueline Graham as Lorna Gant

Nicholas Shields as Christopher Gant

Sarah Gibney as Lisa Kozenczak

Aviva Magner as Debbie Kozenczak

Maureen McRae as Mrs. Trask

Timm Zemanek as Mr. Trask

Maria Ricossa as Helen Gacy

Darryl Palmer as Sheriff

Peter Langley as Mr. Miklovich

John Friesen as Detective #1

Ray Paisley as Illinois K-9 Officer

Brett Halsey as Stan Wilder

Elliott Smith as Gas Station Attendant

David Gardner as Judge

David Bolt as Asst. Principal Burke

Thomas Hauff as Foreman Hendricks

David McAree as Older Worker

J. Winston Carroll as Sergeant on Wabash Ave.

Don Ritchie as Detective on Shakespeare Ave.

Rudy Webb as Cemetery Staffer

Robbie Rox as Cicero Bar Owner

Larry Reynolds as Finger Lake Proprietor

Veliko Pajkovic as Man at Bus Station

John Granik as Narrator (voice)

Luis Guzmán as Waiter (uncredited)

Peter Kerenyi as Pool Player (uncredited)