The burning house at the beginning of the film was a bit of serendipity for the film's crew. The local fire department was burning down an old house to practice putting out the fire, and agreed to let the filmmakers set up and film the event.
According to George A. Romero the only problem that ever came up with the people of Evans City, where the film was being shot, was about the filming of the final scene. In the conclusion Col. Peckem has to strip down and change clothes before being lifted off by the helicopter. Some of the locals saw the scene as it was being shot and took offense to the sight of a nude man outside. Romero said lawyers had to be called in to resolve the issue.
Director George A. Romero makes two cameos in the film; the first as a local being herded into the high school and the second as the head of the president of the United States seen on a monitor screen.
The basis of the film was a script by Romero's friend and co-worker Paul McCollough entitled 'The Mad People'. McCollough gave the script to Romero with his blessing to re-write it and Romero turned out a revised version of it that was made into 'The Crazies'.
In the opening scene, Special Effects Technician for The Crazies, Regis Survinski plays the insane father who murders his wife and torches the house. The children of Cinematographer S. William Hinzman play the terrified kids in the scene. The house was originally slated for destruction by the local fireman as a practice run and Romero got permission to film the burning of it.
Of the three Romero movies Richard France was in, this is the only one where he appears "in person." In There's Always Vanilla (1971) and Dawn of the Dead (1978), he's exclusively shown or heard on television.