Primary and secondary porphyrinemias are characterized by the presence of several porphyrin species in erythrocytes and/or plasma. Acid solvent extraction of porphyrins from natural ligands can preclude observation of significant spectral differences apparent on direct spectrofluorometric examination of porphyrin complexes in tissue. Erythrocytes and Hb-free plasma obtained from 13 patients with erythropoietic protoporphyria, 9 with Pb intoxication, 5 with porphyria cutanea tarda, 3 with Fe deficiency anemia, 1 with erythropoietic porphyria and 10 normal persons were simply diluted and analyzed spectrofluorometrically. Characteristic porphyrin-ligand spectral patterns were consistently obtained for each group of specimens, allowing diagnostic application of the data.