We studied prevalence of attention deficit hyperactivity disorder (ADHD) in senior schoolchildren of Nefteyugansk (Khanty-Mansysky autonomic region) it was 8% (13% among boys and 3% among girls). Clinical examination of 122 children, aged 6-11 years, revealed that risk factors for ADHD were perinatal CNS injures, familial predisposition, unfavorable social and psychological influences. Neuropsychological, neurophysiologic (electroencephalography) and biochemical study showed mild neurological disturbances, some peculiarities of motor and emotional spheres and higher mental functions. Moreover, there were such biochemical alterations as a decrease of magnesium level in the plasma and erythrocytes and a reduction of Mg(2+)-ATPase activity. The use of MAGNE-B6 allowed us to correct many of the disturbances.