To determine the effects of Ramadan fasting on the secretion of sex hormones in single healthy males, we measured blood hormone levels of testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in 52 single male students aged 18-24 years who were fasting for > or = 12 hours during Ramadan. Four blood samples were taken from each, one 2 days before and the others on 10, 20 and 28 Ramadan. Testosterone level was lower, significantly so for the 20th and 28th of the month (P < 0.05); FSH was increased, significantly for the 20th (P < 0.05); LH did not change significantly.