Studies about the relationship of apolipoproteins (apo) and metabolic syndrome in children are scarce. In this study, we analyze apo levels and determine the best cutoff point of the apoB/A-I ratio to diagnose dyslipidemia in prepubertal children with metabolic syndrome.A community-based, cross-sectional study that enrolled 337 children with Tanner stage 1 and average age and body mass index of 9.7±1.6 years and 19.2±3.8 kg/m(2) was carried out. Diagnosis of acute or chronic illnesses constituted the exclusion criteria; in addition, children undergoing medical treatment or receiving vitamins and/or oral supplements were not included.Metabolic syndrome was identified in 42 (12.5%) children (19 girls and 23 boys). The mean apoB/A-I ratio in the children with metabolic syndrome was 0.67±0.18. The best cutoff point of the apoB/A-I ratio for recognizing dyslipidemia was 0.60 (area under the receiver operating characteristic curve, 0.778; sensitivity 80%, specificity 55%). A total of 102 children exhibited apoB/A-I ratio ≥0.60. Diagnosis of metabolic syndrome was performed in 42 (41.2%) children. Among children with metabolic syndrome, 38 (90.5%) had hypertriglyceridemia, 34 (81.0%) low high-density lipoprotein cholesterol (HDL-C), 32 (76.2%) hypertriglyceridemia+low HDL-C, and 40 (95.2%) an apoB/A-I ratio ≥0.60.Our results show that the best cutoff point of the apoB/A-I ratio for recognizing dyslipidemia in prepubertal children is 0.60 and that among children with metabolic syndrome, an apoB/A-I ratio ≥0.60 is the marker of dyslipidemia with the highest frequency.