Two hundred seventy-five patients who had received bleomycin were examined for evidence of pulmonary toxicity. Twenty-six patients were diagnosed as having bleomycin pulmonary toxicity and, of these, 20 (77%) were documented as having renal dysfunction without other features recognized to be associated with the development of pulmonary toxicity. In this study renal dysfunction was a most important factor in the development of bleomycin pulmonary toxicity. As bleomycin is often administered with nephrotoxic drugs, it is suggested that renal function should be checked prior to each administration of bleomycin. It is proposed that appropriate dose modifications could significantly reduce the morbidity and mortality associated with bleomycin administration.