Horror Express

Peter Cushing arrived in Spain for filming and immediately informed producer Bernard Gordon that he could not proceed with the picture, as he felt it was too soon after his wife Helen's death in January 1971. Sir Christopher Lee convinced Cushing to remain on the project by reminiscing with him about the numerous previous films they had worked on together, much to the relief of Gordon. The two actors had by that point appeared together in more than a dozen productions, primarily through their long association with Hammer Film Productions dating to The Curse of Frankenstein (1957). Cushing had entered a period of deep grief following the loss of his wife, and his personal correspondence from the period describes his difficulty resuming professional obligations. The completed film marked one of the actors' more warmly regarded pairings outside the Hammer catalogue, with the extended dialogue scenes between their characters reflecting the personal rapport that Lee's intervention preserved during the early days of the shoot.

The opening credits say the movie takes place in Peking, but all the railroad station sets have signs that say "Shanghai" in Chinese. The cast's dialogue also refers to their train trip starting in Shanghai.

In the opening credits of the English-language VHS version, Christopher Lee's name is misspelled as "Cristopher".

A DVD released by Image Entertainment runs 88 minutes, representing the original theatrical version of the film. A separate DVD released by Simitar Video runs 85 minutes, representing the television version. The three-minute reduction in the Simitar television version reflects standard broadcast edits applied to the print prior to its home video release.