BACKGROUND There is growing evidence to show that atopic diseases are more common in Western Europe than in the former socialist countries of Eastern Europe. OBJECTIVE The aim of this study was to assess whether a similar difference exists between the most eastern province of Finland and a neighboring western district of Russia. METHODS A random sample of 25- to 54-year-old subjects was taken from the population registers in the North Karelia Province in eastern Finland and from the Pitkäranta district across the border in the western part of Russia. Participants filled out a questionnaire on atopic and allergic symptoms and participated in a clinical study, which included skin prick tests with 11 airborne allergens and IgE measurements. RESULTS Self-reported hay fever, allergic eye symptoms, atopic eczema, and asthma were much more common in Finland than in Russia. In Finland 34.2% and in Russia 21.8% had at least one positive skin prick test reaction. In Finland 21.5% but in Russia only 15.8% had at least one elevated allergen-specific IgE value of the 5 values measured. From 6% to 47% of the differences in self-reported symptoms between the countries were explained by atopy, as measured by means of skin prick testing or specific IgE values. CONCLUSIONS A major difference in clinical allergic diseases and signs of symptoms was observed between the 2 geographically adjacent areas. This suggests that the difference in clinical allergy and atopic disposition is related to the differences in lifestyle and environmental factors.