Objective: To analyze the relationships between sleep duration, obstructive sleep apnea syndrome (OSAS), and markers of insulin resistance in obese children. Study design: Forty obese children were evaluated for sleep-related complaints. Each child underwent a polysomnogram, an oral glucose tolerance test (OGTT), and fasting lipid panel tests. Indices of insulin resistance (HOMA-IR and WBISI) and insulin secretion (IGI) were calculated based on the results of the OGTT. Markers of insulin resistance were compared among groups categorized according to polysomnogram results. Results: Subjects with shorter sleep duration had higher fasting insulin, peak insulin, and HOMA-IR levels and lower WBISI levels, findings suggestive of insulin resistance. In contrast, differences in body mass index s scores were not observed. Subjects with OSAS (32 of 40 children) had. higher triglyceride levels and HOMA-IR values than those without OSAS, but did not differ in sleep duration. Multiple linear regression analysis revealed that HOMA-IR was significantly correlated with age, sleep duration, and percent-age of rapid-eye-movement sleep. Conclusions: Insulin resistance in obese children is associated with short sleep duration and OSAS.