- Humphrey Bogart - Dr. Walter Garrett
-Rosemary Lane-Joan Ellwood
- Wayne Morris - Ross Kendrick
- Dennis Morgan - Dr. Ted Steele
- John Litel - Dr. Francis Flegg
- Olin Howlin - Dr. Bill Carrington
- Marguerite Chapman - Alice, la secretaria de Ross
- Huntley Gordon - Dr. Gibbs
- Charles Wilson - Dr. Wells