['To examine the hypothesis that vitamin D deficiency (VDD) is associated with an increased prevalence of microvascular complications in young people with type 1 diabetes.', 'In a cross-sectional study of 517 patients, 25-hydroxyvitamin D was measured. Retinopathy was assessed by 7-field stereoscopic retinal photography, peripheral neuropathy by thermal and vibration threshold testing, and microalbuminuria by albumin excretion rate or albumin-to-creatinine ratio.', 'Retinopathy prevalence was higher in cases with VDD versus sufficiency (18 vs. 9%, P = 0.02); deficiency was not associated with microalbuminuria or neuropathy. In logistic regression, retinopathy was associated with VDD (odds ratio 2.12 [95% CI 1.03-4.33]), diabetes duration (1.13, 1.05-1.23), and HbA(1c) (1.24, 1.02-1.50).'] Is vitamin D deficiency associated with retinopathy in children and adolescents with type 1 diabetes?