The producers used a very William Castle-like exploitation gimmick; plastic packets of "instant blood" were given out to each patron as they entered the theater in case they were attacked by flesh eaters.
According to writer/producer Arnold Drake, Terry Vantell - aka Terry Curtis, wife of director Jack Curtis - won $72,000 on the television quiz show High Low Quiz (1957). Some of the money was used to finish this production.
The original title of the classic zombie film Night of the Living Dead (1968) was "Night of the Flesh Easters". The distributor changed it, so it wouldn't be confused with this film.
Writer/producer Arnold Drake said he got the inspiration for this story from an incident in the 1950s in which millions of dead fish were washed ashore by red-colored tides along the shores of Florida, Georgia and South Carolina.
Pay careful attention to the sound that the flesheaters make. It's very similar (if not the same) as the sound the ants make in Them! (1954).