Based on the methods of the Brain Stroke Register, a study was made of epidemiology and risk factors (RF) of ischemic brain stroke (IBS) in one of the cities of the Middle Ob region, numbering 220 thousand population. Based on 615 cases of IBS, a noticeable rise of the disease incidence was revealed in a group of subjects aged 40-49 years as was a high level of the morbidity and mortality among persons over 60 years. Studies into RF discovered a high portion of arterial hypertension (75.1%), atherosclerosis (44.3%), aggravated heredity (28.6%), coronary heart disease (27.9%), alcohol abuse (17.9%). In 90.8% of cases, IBS developed in the presence of unfavorable fluctuations in atmospheric pressure, relative humidity, temperature, and the rate of air movement.