Mice were stained with pulverized charcoal and the resulting grooming behaviour observed. From 119 controls, the typical patterns indicated a late cleaning of the tail, the sacrum and the region between the ears. The following substances were tested: Imipramine, Desipramine, Trimeprimine, Amitriptyline, Nortriptyline, Chlordiazepoxide, Iproniazide, d-Amphetamine, Chlorpromazine, Haloperidol, Acetylsalicylic acid, Metronidazole. Of these Amitriptyline, Chlorpromazine, Haloperidol and Metronidazole were effective in doses less than 1/10 of LD 5. © 1969 Springer-Verlag.