Trivia

Filmed in 1966, not released in the United States until December 1969.

Jack Palance dubbed the English voice of Riccardo Garrone's character Matteo Cirini.

Shown on a double-bill with Fearless Frank (1967) in its original U.S. release.

Interiors were largely shot in Spain, exteriors in Italy.

Cesar Romero replaced George Raft, who had become ill, in the title role of Mike Madigan. None of Raft's scenes remain in the film.