The relative distribution of radioactivity after i.v. (5 mg/kg) and oral (25 mg/kg) application of 14C-Zolimidine [2-(p-methyl-sulfonylphenyl)-imidazo-(1,2-a)-pyridine-2-14C] was examined in male rats by whole-body autoradiography and scintillation fluid spectrometry. 14C-Activity was remarkably concentrated in the stomach of i.v. treated animals, probably as a result of secretion from the pyloric and/or fundic part of the mucous membrane. 14C-Zolimidine also accumulated in the aortic vascular walls, the adrenal gland, and in the excretory organs, liver, kidney, and intestine, after both routes of drug administration. Much less radioactivity could be measured in brain and spinal cord. The estimation of nearly 80% gastrointestinal absorption of 14C-zolimidine and the suggestion of one or more metabolites were in accordance with previously reported results. The elimination of radioactivity from brain occurred more rapidly than from other organs. No striking results were found in the reproductive organs of the rats.