OBJECTIVE To evaluate HbA(1c) followed from diagnosis, as a predictor of severe microvascular complications (i.e., proliferative diabetic retinopathy [PDR] and nephropathy [macroalbuminuria]). RESEARCH DESIGN AND METHODS In a population-based observational study, 447 patients diagnosed with type 1 diabetes before 35 years of age from 1983 to 1987 in southeast Sweden were followed from diagnosis until 2019. Long-term weighted mean HbA(1c) (wHbA(1c)) was calculated by integrating the area under all HbA(1c) values. Complications were analyzed in relation to wHbA(1c) categorized into five levels. RESULTS After 32 years, 9% had no retinopathy, 64% non-PDR, and 27% PDR, and 83% had no microalbuminuria, 9% microalbuminuria, and 8% macroalbuminuria. Patients with near-normal wHbA(1c) did not develop PDR or macroalbuminuria. The lowest wHbA(1c) values associated with development of PDR and nephropathy (macroalbuminuria) were 7.3% (56 mmol/mol) and 8.1% (65 mmol/mol), respectively. The prevalence of PDR and macroalbuminuria increased with increasing wHbA(1c), being 74% and 44% in the highest category, wHbA(1c) >9.5% (>80 mmol/mol). In comparison with the follow-up done after 20-24 years duration, the prevalence of PDR had increased from 14 to 27% and macroalbuminuria from 4 to 8%, and both appeared at lower wHbA(1c) values. CONCLUSIONS wHbA(1c) followed from diagnosis is a very strong biomarker for PDR and nephropathy, the prevalence of both still increasing 32 years after diagnosis. To avoid PDR and macroalbuminuria in patients with type 1 diabetes, an HbA(1c) <7.0% (53 mmol/mol) and as normal as possible should be recommended when achievable without severe hypoglycemia and with good quality of life.