Saul Bass had a fascinating career as an animator and as designer of title sequences for a number of notable films, including Psycho, Vertigo, Anatomy Of A Murder and Seconds. However, Phase IV was his only credit as director of a feature film. A visually inventive science-fiction story, Phase IV concerns a group of research scientists working in the Arizona desert who find themselves confronted by an Army of super-intelligent mutant ants. The results are more intelligent than the description would lead you to believe, and Nigel Davenport and Michael Murphy turn in good performances as the embattled men of science.
~ Mark Deming, All Movie Guide