The incidence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in Lebanon is estimated at 10 per 1,000 in men and 0.4 per 1,000 in women. A community-based cluster sampling survey was conducted in 15 villages in all areas in Lebanon. The survey found 36 cases of G6PD deficiency among 3,000 men aged 14 years and above, yielding a cumulative incidence rate of 12 per 1,000. Of those 36 cases, 28 (77.8%) knew of their problem since they had already suffered at least one severe anaemia crisis in their childhood following the ingestion of raw green fava beans. The remaining 22.2% were not aware at all of their defect. These findings confirm that G6PD is a common genetic problem in Lebanon. The efficiency of early screening programmes in terms of preventing severe, at times potentially lethal, haemolytic crises is currently being investigated.