In recent years several studies in children and adults have shown an increase in prevalence of atopic diseases in East and West Germany. The observed frequency of allergic diseases, however, was significantly lower in the East compared to the West. Using data of the German National Health Interview and Examination Survey 1998 and of National Surveys from 1990/92 it was examined, whether the reported increase in prevalence could be confirmed for the total population and whether the differences between East and West are still present. In a self-administered questionnaire, study participants were asked whether they have ever had hay fever. Additionally, in a physician's interview, subjects were asked whether a physician had ever diagnosed hay fever. The questionnaire data were used in comparison with the previous national surveys for the calculation of time trends. A total of 6974 persons filled in the questionnaire and 7099 persons took part in the interview. Physician-diagnosed hay fever was reported by 15% of the total study population. Clear differences in the prevalence rates between East and West Germany are still existing; 11% in the East and 17% in the West suffer from hay fever. In both parts of the country prevalence decreases with increasing age. The highest rates were found among those aged 20-29 and 30-39 years. Based on the questionnaire data the morbidity rose from about 10% in 1990/92 to 17% in 1998. The overall relative increase is quite comparable in East and West Germany. Stratification by age and gender shows considerable differences. In young women from East Germany the increase in prevalence is substantially higher and in women aged 40 years or older much lower than in West German women. In men this pattern has not been observed.