Quite uniquely, director François Truffaut chose to shoot the film almost completely in chronological order. The reasoning for this was that he found the relationship between the two main characters so important, he wanted it to develop in a natural way. Truffaut actually spent the nights re-writing the scenes he would film the next day, to follow the dynamics between the leading couple.
The film is dedicated to director Jean Renoir. The dedication is visible at the beginning and signed by Truffaut.
The original French title is spelled "La Sirène du Mississipi" (one P) in some sources, and "La Sirène du Mississippi" (two Ps) in other sources.
The book that Louis finds in the isolated cabin near the end of the movie is "La Peau de chagrin" ("The Wild Ass's Skin"), by Honore de Balzac. According to Wikipedia, "Set in early 19th-century Paris, it tells the story of a young man who finds a magic piece of shagreen (untanned skin from a wild ass) that fulfills his every desire. For each wish granted, however, the skin shrinks and consumes a portion of his physical energy."
The least-known of Francois Truffaut's films in the UK. Although it was shown in France in 1969 and had a showing at the Edinburgh Film Festival the following year, it gained no commercial distribution whatever in Britain until 1974, when a cut version dubbed into English, intended to be exhibited as the lower half of a double-bill, was press-shown, although it seems to have been shown hardly anywhere at that time. The proper French version was shown on BBC-2 a few years later, but this was its only British television showing. Despite the fame of its director and stars. the film remained largely unknown in the UK until a 21st-century DVD release.