Abstract Background Peripubertal hyperandrogenemia (HA) often represents a forerunner to adolescent/adult polycystic ovary syndrome (PCOS), but risk factors for peripubertal HA are unclear. Studies have associated obesity with HA throughout puberty (e.g., McCartney, JCEM 2007;92: 430-436, Knudsen, Obesity 2010;18: 2118-2124). However, these studies were performed in academic centers and could have been influenced by recruitment bias. We therefore investigated if there was a difference in calculated free testosterone (T) levels between girls with healthy weight and those with obesity in a nationally-representative U.S. sample. Methods We analyzed data for 1,196 girls aged 6–18 years from the National Health and Nutrition Examination Survey (NHANES) 2013-2016 databases, utilizing a cross-sectional study design. We calculated free T from total T and sex hormone-binding globulin (Vermuelen equation). We divided girls into 3 groups by age, based on presumed pubertal stages: "Pre-/Early" (6–9 years), "Middle" (10–14 years), and "Late" (15–18 years). Each individual was also categorized as healthy-weight (BMI-for-age percentile 5-85) or obese (BMI-for-age percentile ≥95). We analyzed mean free T concentrations by weight status (healthy-weight vs. obese) for each age group by calculating population estimates. We also performed survey-weighted regression analysis to assess the relationships between weight status and age category (independent variables) and free T (outcome). Results Among Pre-/Early girls, free T was 0.33 pg/ml (0.28-0.38) [mean (95% CI)] for healthy-weight vs. 0.86 pg/ml (0.67-1.05) for obese. Among Middle girls, free T was 2.53 pg/ml (2.27-2.78) for healthy-weight vs. 4.35 pg/ml (3.75-4.95) for obese. Among Late girls, free T was 3.33 pg/ml (2.96-3.70) for healthy-weight vs. 5.64 pg/ml (4.93-6.36) for obese. (Notably, in each age group, the 95% CIs for free T did not overlap between healthy-weight vs. obese subgroups). Mean free T increased with advancing age in both healthy-weight and obese groups, especially between Pre-/Early and Middle age ranges (Pre-/Early-to-Middle differences were 2.20 pg/ml for healthy-weight and 3.49 pg/ml for obese). Our regression model accounted for 45% of the variance in free T (R2=0.45). Both weight status (obese vs. healthy-weight) and age group were independent predictors of free T concentrations (p<0.0001 for both). When adding an age-in-months-by-BMI-percentile interaction term, the model R2 value was 0.47, with age category, weight category, and the interaction term all being independent predictors of free T (p<0.001 for all). Conclusion We conclude that obesity is associated with higher free T levels in U.S. girls aged 6–18 years. Age also predicts free T, likely reflecting increases related to pubertal maturation, and free T differences according to weight status are more prominent in older girls. This study in a nationally-representative sample of U.S. girls supports previous analyses of girls studied at academic centers, further suggesting an important relationship between obesity and peripubertal androgen excess. Presentation: Sunday, June 12, 2022 11:00 a.m. - 11:15 a.m.