The Irkutsk province and the Republic of Buryatia which are a part of the Baikal Region (Siberia) were studied for environmental iodine balance. The water and local foodstuffs were found to show low iodine levels (they being 0.2 to 6.9 micrograms/l). In children, iodine deficiency was detected in 60-87% of the total number examined. There was a relationship between of the severity of neurological symptoms, the onset of thyroid diseases, general morbidity, physical development, iodine levels in the body. It is concluded that iodine deficiency has a great impact on the development of the regional pathology in children.