Several studies based on psychometric tests have determined an impairment of cognitive functions in patients with androgen deficiency. However, little is known about event-related potentials (ERPs) alterations in male hypogonadism. We investigated alterations of ERP in male hypogonadism before and 3 months after gonadotropin treatment. ERPs were elicited in 20 untreated male patients with idiopathic hypogonadotropic hypogonadism (IHH) (mean age: 21.1+/-1.4 years) and in a group of 30 male controls with comparable mean age and educational level. ERP recordings were repeated 3 months after hCG/hMG treatment. Untreated hypogonadal patients had longer mean P300 latencies and increased P300 amplitudes when compared to those in controls (321.6+/-18.5 vs 299.3+/-20.1 msec, p=0.0002; 12.15+/-4.47 vs 9.38+/-3.02 microV, p=0.011, respectively). The mean P300 latencies did not change significantly 3 months after gonadotropin treatment, while P300 amplitudes were decreased significantly. P300 latencies did not correlate with serum testosterone and other hormone levels. We conclude that prolongation of P300 latencies and increased P300 amplitudes are associated with male hypogonadism, but P300 prolongation is not reversed 3 months after gonadotropin treatment. These findings confirm the occurrence of cognitive defects in hypogonadal patients and would support the hypothesis that perinatal androgen deficiency contributes to an insufficient cognitive development.