Altered States is a superbly silly movie, a magnificent entertainment, and a clever and brilliant machine for making us feel awe, fear, and humor.

Roger Ebert

Chicago Sun-Times

Not one to let slow-building tension and mystery get in the way of wild flourishes of extremism and shock, Ken Russell hit upon a story that more or less handled his structural excesses and tendency toward blasphemy.

Ian Nathan

Empire

The film is in fine shape as long as it revels in its own craziness, making no claims on the viewer's reason. But when it asks you to believe that what you're watching may really be happening, and to wonder what it means, it is asking far too much.

Janet Maslin

The New York Times