The condition diagnosed as porphyria cutanea tarda in adults began with bullous lesions which progressed to ulceration and generally healed, leaving pigmented scars characterized by the presence of microcysts. In children, the initial lesions resembled comedones and milia. In severe cases the picture was that of "monkey disease." Porphyrinuria appeared early, and the systemic effects were sometimes serious and permanent. More than 600 cases were observed durin a 5-yr period in the southeastern region of Turkey, and the total incidence is estimated to have exceeded 3,000. The outbreak was traced to the consumption of wheat as food, contrary to plan, after it had been prepared for planting by treating it with a fungicide, hexachlorobenzene.