PURPOSE: This study was undertaken to identify the frequencies and the risk factors of microvascular complications in subjects with type 1 diabetes mellitus METHODS: The frequencies and their relation to risk factors of microvascular complications were analyzed in 29 type 1 diabetes mellitus subjects with duration of disease more than 5 years. Microvascular disease was defined as the presence of either retinopathy, microalbuminuria or neuropathy. RESULTS: The overall prevalence rate of microvascular disease was 8/29(27.6%). Retinopathy has developed in 3 patients(10.3%), microalbuminuria in 7 patients(24.0 %) and neuropathy in 5 patients(17.2%). The mean HbA1C was significantly higher in the patients with microvascular complications(11.6+/-.2% in microvascular complication group vs 9.3+/-.6% in control group). CONCLUSION: In childhood onset type 1 diabetes mellitus, poor glycemic control is an important risk factor for microvascular complications.