Human albumin catalyzed the in vitro transformation of prostaglandin D2 into three novel dehydration products identified as 9-deoxy-11-keto-15 alpha-hydroxy-delta-5,9,12-prostenoic acid; 15-deoxy-11-keto-9 alpha-hydroxy-delta 5,9,12,14-prostenoic acid. Results suggest that albumin can influence, qualitatively and quantitatively, the metabolism of eicosanoids.