[en] Accumulation of a radioactive label in tumor tissue is required for scintigraphic visualization of the tumor and has been achieved by application of bleomycin as carrier. This chemotherapeutic polypeptide drug has been labeled with ⁶⁴Cu. Thin layer chromatography of ⁶⁴Cu-bleomycin which was incubated for 22 hours at 37⁰C showed no changes of the chelate. When urine of the ⁶⁴Cu-bleomycin treated animals was chromatographed considerable amounts (9.3%) of free ⁶⁴Cu appeared 2 hours after injection of the chelate and dissociation was found to be almost complete 4 hours after injection of labeled bleomycin. The distribution of ⁶⁴Cu-bleomycin is similar to that found with sup(99m)Tc-bleomycin with long lasting accumulation in kidneys and liver. Highest concentration ratios of the activity in mesenchymal tumor (Yoshida) and blood respectively were found 6 hours after intravenous administration of ⁶⁴Cu-bleomycin. (author)