The correlation between the chromodacryorrhea and the excess porphyrin formation by the Harderian gland of pantothenic acid-deficient rat was examined. It was thereby found that the main porphyrin in the red tears on pantothenic acid-deficient rats was not coproporphyrin, reported by McElroy, et al., but was protoporphyrin-IX, thin-layer chromatographycally and spectrophotometrically. According to the measurement of porphyrin content and δ-aminolevulinic acid synthetase (succinyl-CoA : glycine C-succinyl-transferase (decarboxylating), EC 2.3.1.37) activity in the Harderian gland, it was assumed that the chromodacryorrhea was caused by secretion of excess protoporphyrin formed due to the increase in δ-aminolevulinic acid synthetase activity and the hypertrophy of Harderian gland.