Vitiligo, morphologically indistinguishable from true vitiligo, was detected in 54 of 198 men exposed to p-tert-butylphenol (P.T.B.P.) during its manufacture. There is evidence that P.T.B.P. caused vitiligo by a systemic mechanism and that the severity of the disease was related to the intensity of exposure. No association with autoimmune disease was found. Screening for other possible associated disorders revealed mildly abnormal liver-function tests in 6 workers: liver biopsy confirmed liver damage. Of the 144 men exposed to P.T.B.P. who did not have vitiligo, only 2 had any abnormal liver-function test. It seems possible that the liver damage is related to P.T.B.P.