In matriculation examinations at age 16, girls achieved greater score than boys. It is still uncertain whether gender gap in examination achievement reflects sex difference in fundamental cognitive domains or not. This cross sectional comparative study was undertaken to determine the cognitive ability in 62 male and 62 female medical students between 16-22 years of age attending in University of Medicine (2) Yangon with body mass index within 18.5-24.9 kg/m2. Blood haemoglobin concentration was determined by cyamet-haemoglobin method. Serum ferritin concentration was measured by enzyme linked immunoassay method.