Medical schools, at least as late as the 1980s, showed clips from this movie to illustrate various concepts in human anatomy, physiology, and especially immunology.
When filming the scene where the other crew members remove attacking antibodies from Raquel Welch for the first time, director Richard Fleischer allowed the actors to grab what they pleased. Gentlemen all, they specifically avoided removing them from Welch's breasts, with an end result that Fleischer described as a "Las Vegas showgirl" effect. He pointed this out to the cast members - and on the second try, the actors all reached for her breasts. Finally, Fleischer realized that he would have to choreograph who removed what from where, and the result is seen in the final cut.
The time spent in the movie of the crew once they are miniaturized takes up almost exactly one hour of the movie.
During filming, one of the two three-inch "Proteus" models used in the miniaturization sequence was left by an open window and was subsequently carried off by a crow.
Raquel Welch said in her 2013 book that she was infatuated with Stephen Boyd in making this movie, although he declined her advances.