With the aim to study potential risk factors for the development of microalbuminuria and retinopathy, baseline characteristics were examined in 50 Brazilian IDDM patients followed for 4.48 years with a 2-year reexamination. During the study, 3 patients (6%) aged 25.9 +/- 4.4 years, duration of diabetes 8.1 +/- 4.2 years, died from acute complications without microalbuminuria and retinopathy after a follow-up of 2.1 +/- 0.7 years. The standardized mortality rate for the group was 0.84 per 1000 (95% CL, 0.31, 1.83) in comparison to 0.14 per 1000 in the general population. From 34 normoalbuminuric individuals at baseline (urinary albumin excretion rate (AER) < or = 20 micrograms/min in > or = 2 overnight urine collections), 10 developed microalbuminuria with an incidence density of 6.5 cases per 100 person-years (95% CL, 2.23, 10.16). Spontaneous normalization of AER was found in 2 of 4 patients with microalbuminuria at cycle 2. Multiple stepwise regression analysis demonstrated that baseline AER (p = 0.03), but not glycated hemoglobin, blood pressure or duration of diabetes, predicted end-of-study AER. From 36 patients without retinopathy, 10 developed nonproliferative retinopathy with an incidence density of 6.6 cases per 100 person-years (95% CL, 2.75, 10.54). Retinopathy was associated with duration (p = 0.05) and age at diagnosis of diabetes (p = 0.01). A tendency with baseline AER (p = 0.06) was also noted. No patient developed macroalbuminuria, proliferative retinopathy or hypertension. By the end of our study, in a cohort of young IDDM patients followed in a developing country, 6% died from acute complications and 15 patients (44.1%) developed retinopathy and/or microalbuminuria. Our results suggest that the only predictor of end-of-study AER was baseline AER. Also, duration of diabetes and age at diagnosis appear to be risk factors for retinopathy.