It was recently suggested that there is a tendency of the rising incidence of diabetes type 1 in different countries in Europe. In our previous studies we observed the high frequency of ICA among first degree relatives of diabetic subjects, what could suggest a rapid increase in the incidence of diabetes type 1 also in the north-eastern region of Polan. The aim of the study was to estimate the annual incidence of diabetes type 1 in the north-eastern region of Poland and to evaluate the association of the incidence rates with the age, gender, urban-rural differences and the season of the year of the disease onset. The register of new cases of IDDM was established in 1994 using 2 independent data sources. The degree of ascertainment was 98.9% for the combination of both data sources. We observed a rising trend in the incidence from 6.4 in 1994 to 9.9 cases per year per 100,000 in 1998 (p < 0.001). The highest incidence rate increase was recorded in boys aged 5 to 14 years old (16-17 cases per 100,000 in 1997-1998). The rising trend in this incidence was observed in the rural areas, while in urban populations the incidence was unchanged. Seasonal variation in the incidence was also recorded, with a peak in autumn and winter and nadir in summer. Our observations suggest the necessity of the continuation of the studies to identify the diabetogenic environmental factors and to try preventive procedures in the studied population.