Objective: To evaluate the epidemiologic, clinical and laboratory characteristics of a group of children with type 1 diabetes mellitus (T1DM) living in a Turkish city. Methods: The records of 395 (boys/girls: 199/196) children with newly diagnosed T1DM hospitalized in the years 1985-2004 were evaluated retrospectively. The data were assessed by gender and age subgroups (<=5, 6-10 and >=11 years).Results: Mean age of children at diagnosis was 8.1±4.1 years. At T1DM onset, the number of children <=5, between 6-10 and >=11 years old was 110 (27.9%), 147 (37.2%) and 138 (34.9%), respectively. The patients were mostly diagnosed at ages 6-8 years (24.1%), followed by cases aged 3-5 years (22.0%). Polyuria and polydipsia were the most common symptoms (94.7%). Mean duration of symptoms was 21.5±18.6 days. Although the patients mostly presented in autumn (30.7%), no season-related significant differences were found. The frequency of ketoacidosis was relatively high (48.5%). When compared to boys, the girls experienced higher rates of ketoacidosis (55.1% vs. 41.7%, p=0.042); had a higher frequency of antithyroid peroxidase antibodies (11.7% vs. 4.2%, p=0.049) and higher insulin requirement (0.89±0.41 vs. 0.77±0.36 IU/kg, p=0.005). Cases with a family history of T1DM were more likely to have anti-endomysial antibodies (42.9% vs. 8.1%, p=0.027) and higher initial blood glucose levels (510.5±145.0 vs. 436.1±156.5 mg/dL, p=0.005).Conclusion: The findings possibly indicate a decreasing age of T1DM onset. The high frequency of ketoacidosis at presentation is noteworthy. Girls had higher rates of ketoacidosis, higher frequency of anti-thyroid antibodies and higher insulin requirements as compared to boys. Patients with a family history of T1DM had higher initial glucose levels and higher frequency of antiendomysial antibodies