HbA1 was determined in 15 G-6-PD-deficient subjects during a hemolytic crisis with hemoglobinuria due to ingestion of fresh fava beans. The same G-6-PD-deficient subjects were studied again 4 months after the crisis, when they were asymptomatic. 15 normal healthy children served as controls. A statistically significant decrease in HbA1 was observed in the favic subjects during hemolytic crises compared with their values 4 months later and those of the control group.