Childhood depression, anxiety, and aggression assessment instruments were examined in a sample of 8- to 11 -year-old elementary school children. A multitrait-multimethod design was used to evaluate self-, parent-, teacher, and peer-report on each of the three traits. Results found the measures exhibited significant convergent and discriminant validity for both boys and girls. However, different patterns in convergence among the information sources emerged between boys and girls. Both the intercorrelations and the analyses of variance documented significant method variance. The implications of the high method variance or source bias in the assessment process are discussed. It is argued that investigators employ confirmatory factor analyses in evaluation of muititraitmultimemethod data.