OBJECTIVE To assess the prevalence of abnormal vitamin D status in children and adolescents with chronic kidney disease (CKD). METHODS This was an outpatient cross-sectional, retrospective study of 258 patients, mean age 12.3 +/- 5.2 years, with an average estimated glomerular filtration rate (eGFR) of 106 +/- 51 mL/min/1.73 m2 (range, 0 to 220 mL/min/1.73 m2). Serum 25-hydroxy-vitamin D [25(OH)D], calcium, phosphorus, and parathyroid hormone levels, as well as selected anthropometric variables, were analyzed. RESULTS Reduced 25(OH)D concentrations (< 30 ng/mL) were found in 60% of the patients. In 28%, the concentration was < 20 ng/mL, indicating vitamin D deficiency. Patients with more advanced CKD were more likely to have vitamin D deficiency compared with those with incipient CKD or normal GFR (42% vs 26%; P = .03) and displayed more prominent hyperparathyroidism. Suboptimal vitamin D status was similar in males and females, but was significantly more prevalent in older (P < .01), non-Caucasian (P < .01), and overweight (P = .02) patients. Patients with early-stage CKD (eGFR > 60 mL/min/1.73 m2) and with vitamin D deficiency were significantly shorter than their counterparts with 25(OH)D levels > 20 ng/mL (P = .02). CONCLUSIONS Vitamin D insufficiency and deficiency are very prevalent in pediatric patients across all stages of CKD, particularly in non-Caucasian and obese patients, and may contribute to growth deficits during the earliest stages of CKD.