It has been estimated that during 1955-1959 in southeastern Turkey, approximately 4000 people developed porphyria due to ingestion of hexachlorobenzene (HCB), a fungicide added to wheat seedlings. Patients subsequently developed bullae on sun-exposed areas, hyperpigmentation, hirsutism, weakness and porphyrinuria. Children born to mothers who had ingested the grain were exposed to HCB in maternal milk and transplacentally, resulting in the death of children under the age of two. In this follow-up study, 204 patients with a past history of HCB-induced porphyria were re-evaluated. There were 132 males and 72 females, with an average age of 32.1 years, an average age of onset of 7.1 years and a duration of 2.4 years. The clinical features of the 204 patients were: scarring of the face and hands in 86.7%, hyperpigmentation in 71.1%, hirsutism in 47.1%, pinched facies in 41.2%, fragile skin in 37.7%, painless arthritis in 66.6%, small hands in 64.2%, an enlarged liver in 4.4% and an enlarged thyroid in 37.3%; most patients also showed neurological symptoms. Urine and stool porphyrin levels were determined in all patients. Seventeen showed elevated levels of one of the porphyrins and eight were considered still porphyric after 25-30 years. A total of 56 specimens of human milk obtained from porphyric mothers were analysed for HCB. The average value was 0.51 ppm compared with 0.07 in controls. After HCB ingestion, abnormal porphyrin metabolism, dermatological, orthopaedic and neurological findings, and HCB residues in the milk of porphyric patients have been shown to persist at least for 25-30 years.