Pathological and biochemical examinations were made on tissues from a case of porphyria in a slaughtered pig. Bones, kidneys, teeth and lymph nodes showed a mahogany discoloration. Histologically, the pigment was negative on staining for iron (Gomori) and showed a strong red-orange fluorescence under UV light proving it to be porphyrin. Biochemical studies on the kidney, lymph nodes, bone and bone marrow revealed a 'mixed' erythropoietic protoporphyria-coproporphyria. This indicates that the case presented probably represented both a uroporphyrinogen decarboxylase and uroporphyrinogen-III-cosynthase dysfunction.