Diagnostic application of57Co-bleomycin (57Co.BLM) is considerably limited by the problem of patients urine contamination with the long-lived radionuclide (T1/2=270 days). A method for decontamination of urine using charcoal (Carbosorb pulvis) was tested in 10 patients examinated by the57Co-BLM scan. About 95% of activity excreted into the urine was eliminated during the first 24 hours after injection. An average decontamination efficiency of 91.8% was obtained using the ratio of 10 g of charcoal/litre of contaminated urine. A method for urine decontamination applicable in clinical practice is proposed.