Five hundred apparently healthy adult subjects of both sexes were screened for the presence of glucose-6-phosphate dehydrogenase (G-6- PD) deficiency. The results were analysed comparing its frequency between different ethnic groups, sex and with previous studies in the region. The deficiency was detected in 3.8% (19/500) of a randomly selected population. This is markedly different from previous studies in the region which reported very high incidence in Pathans (8,6%) as compared to Punjabis (2.6%) and in males (2.5%) as compared to females (1.3%). Contrary to the expectation, no statistically significant difference was noted in the prevalence of this defect between the two major ethnic groups: 3.3% in Punjabis (8/245) and 4.0% in Pathans (8/201). We identified high prevalence in `ARAIN' sub group of Punjabi population (5/26, 19.2%; p 0.01). Male to female ratio did not show any statistically significant difference (M: 14/326, 4.3%; F: 5/174, 2.9%). Consanguinity was observed in 64% (9/14) of males and in 80% (4/5) of females.