Introduction: The incidence of type 1 diabetes mellitus (T1DM) has dramatically increased recently in some countries. [Aim: To ascertain any changes in the incidence of T1DM in our population during the years 1990-2004. Methodology: All newly diagnosed cases of T1DM children under the age of 15yr were registered and relevant information was obtained. Population demographic data based on the most recent census were used for calculations. Results: The overall mean annual incidence of T1DM during this 15-yr period was 11.9/100 000 person-years, with a statistically significant increase in the third 5-yr period (14.9/100 000 person-years). The incidence during the first (1990-1994) and second (1995-1999) 5-yr periods was 10.5/100 000 person-years (p<0.001). The overall male:female ratio was 0.94. Seasonal distribution for the first and second 5-yr periods revealed a higher incidence during winter and autumn months. Seasonal variation, however, disappears in the third 5-yr period, where no differences were found between the four seasons. Conclusion: The incidence of newly diagnosed T1DM cases has increased during 2000-2004. A seasonal variation during the first and second 5-yr periods was no longer observed in the third 5-yr period.