[14C] penitrem A (1.1 mg) was given intravenously to a sheep under barbiturate anaesthesia. The radioactivity was almost completely excreted in the bile within four hours but the penitrem had been transformed to more polar products. [14C] penitrem E (4.5 mg) was eliminated similarly. Incubation of the penitrems with sheep or rat liver homogenate did not result in any metabolic products. However, in sheep bile, whether previously boiled or not, complete transformation to more polar products occurred spontaneously within seven hours at 37 degrees C, and apparently non-enzymic process which seems to be a novel attribute of bile.