Pubertal insulin resistance (IR) is well recognized; but little data are available for glucose and insulin pattern from a large, unselected lean population. This report describes the age- and sex-specific distributions of glucose tolerance and IR in a rural Chinese twin population. This report includes 4488 subjects aged 6 to 24 years. The primary variables of interest are fasting plasma glucose, 2-hour postload plasma glucose (2-h PG), fasting serum insulin, 2-hour postload insulin, and the homeostatic model assessment for IR. Age- and sex-specific patterns for the primary variables are described using smoothing plot, arithmetic or geometric mean, and percentiles. There is an increase in fasting plasma glucose, 2-h PG, and IR during puberty (10-19 years) and a return to prepuberty level by the age of 20 years. Insulin resistance peaks at around the age of 14 years in girls and 16 years in boys. Two-hour postload plasma glucose and 2-hour postload insulin are higher in girls than in boys from early puberty, and the sex differences are more pronounced afterward. Moreover, the prevalence of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) increases after puberty and is higher in girls than in boys. In this community-based, nonobese rural Chinese twin population, we observed sex-specific remarkable pubertal surge of IR and modest increase in plasma glucose as well as increasing prevalence of IFG and IGT with age. Notably, females had higher 2-h PG and higher prevalence of IFG and IGT. Our study underscored that adolescence (even more so in females) is a critical period for developing IR and prediabetes.