Lysergic acid diethylamide (LSD-25 Sandoz) given orally in single doses as low as 20 micrograms produces depersonalization, derealization, and increased imagery in "normal" individuals. Larger doses are required to produce the same effect in psychotic patients.Of 15 patients with depressive reactions, 3 recovered and 4 improved after one month's treatment with daily oral doses of 20-100 micrograms of LSD. Four patients showed no improvement. In 4 cases, treatment was discontinued before proper evaluation could be made. Anxiety was a prominent reaction while less frequently euphoria was observed. In 3 patients who developed euphoria it served as an aid to psychotherapy by encouraging expression of feeling. In the others the heightened anxiety encouraged reticence rather than confidence.Improvement obtained during the course of LSD therapy was not greater than that obtained without its use in comparable cases. However, LSD affords therapeutically valuable insights into unconscious processes by the medium of the hallucinations it produces.