Research shows that allylisopropylacetylurea not only increases the amount of porphyrins in the liver and urine of animals but also brings about a marked green pigmentation of the liver. Rats recover well from long-term treatment with high doses of allylisopropylacetylurea and revert to normal values for parameters measured. Lesions originated by long-term administration with allylisopropylacetylurea can be tolerated by rats and are reversible. Fixed drug eruption and mucocutaneous ocular syndrome are reported due to apronal.