[Do not forget: lead poisoning].

3 patients with lead intoxication are demonstrated. The analysis of porphyrins and porphyrin precursors led to the tentative diagnosis which was confirmed by the increased lead levels. The increased urinary excretion of porphyrins and of delta-aminolevulinic acid, the decreased activity of uroporphyrinogen synthase and the increased protoporphyrin content (absorption maximum 595 nm) in the red cells suggested the diagnosis before the lead values of the patients were known. Clinical signs of the patients included gastrointestinal and neurological symptoms. It is assumed that the lead intoxication in these patients was caused by occupational exposition.