Studying the metabolism of drotaverin (No-Spa¿), we have elaborated a method for the isolation, purification and separation of metabolites and of drotaverin excreted in unchanged form in the urine and feces. The structure of the chief metabolites was cleared by t.l.c., polarography, UV spectrophotometry, and mass spectrometry. It was stated that beside drotaverin excreted in unchanged form, the biotransformation of the molecule results in the formation of oxidation and desalkylation products.