ABSTRACT.Clinical and laboratory evaluation of 60 boys with hemizygous, 12 girls with homozygous, and 11 girls with heterozygous erythrocyte glucose‐6‐phosphate dehydrogenase deficiency was made during haemolytic crisis. The main clinical symptoms were paleness, dark urine and oliguria. Only one patient needed peritoneal dialysis. Coexistence of glucose‐6‐phosphate dehyrogenase deficiency associated with haemoglobinopathy was found to be higher than expected (32 out of 83 cases). Also, the high prevalence of glucose‐6‐phosphate dehydrogenase deficiency among females with homozygous and heterozygous disease was surprising. The precipitating factors of haemolysis were variable. Rather than antimalarial and antipyretic‐analgesic drugs, infections seemed to be the main haem