Original advertising art featured a sketch of Alex Cord's character plunging a syringe into his arm - but the needle was covered by a black censorship block when the image was distributed as newspaper ads, poster art and as cover art of the soundtrack album.
Alex Cord's bare-chest scenes in this movie probably qualify as his finest "beefcake" moments on the screen.
Lee Marvin turned down a role.
Originally announced by Columbia in 1964 as a Sidney Poitier vehicle.
Statement in the end notes: "Columbia Pictures is grateful to Synanon for the opportunity to film this picture where it all began."