Compared Child Behavior Checklist results in 103 girls with Turner syndrome (TS) ages 7 to 13 years and 52 age-matched normal girls. Subjects with TS were part of a national study in Canada to evaluate growth hormone therapy in TS. Present data were obtained at baseline. Girls with TS scored below the comparison group in Total Social Competence (p < .0001), and above it in Total Behavior Problems (p < .05), Social (p < .0001), and Attention Problems (p < .001) scales. Item analysis revealed that subjects with TS were more immature, hyperactive, and nervous, and had poorer peer relations, greater difficulty at schooling, and more problems concentrating. In children with TS, height was correlated with social competence while karyotypes involving structural abnormalities of the X chromosome were associated with more behavior problems than a missing X or mosaicism.