The pattern of tryptophan metabolites "via kynurenine" was determined in the epidermis of man and mouse using semiquantitative method of one- and two-dimensional thin-layer-chromatography. In the epidermis of healthy man the following metabolites were present: tryptophan, kynurenine, anthranilic acid, 3-hydroxyanthranilic acid, 3-hydroxykynurenine, kynurenic acid, nicotinic acid; the same metabolites, with the exception of kynurenine, were present in the epidermis of healthy mouse. In the epidermis of patients with porphyria cutanea tarda and of those with pellagra, the above pattern was modified and resulted similar to that found in the urine. In the epidermis of patients with pellagroid erythema an alteration of "via kynurenine" metabolites was present. In epithelioma tissues all the above mentioned metabolites were increased while in keratoacanthoma were normal. In burnt epidermis xanthurenic acid was present. In the epidermis of mouse with DDC-porphyria the pattern was characterised by absence of tryptophan, anthranilic and nicotinic acids. These data and those obtained by determination of tryptophan-pyrrolase and kynureninase activities are presented and discussed.