The genetic and environmental contributions to children’s maladaptive behavior were assessed in a sample of 154 twin pairs (77 monozygotic twin pairs and 77 dizygotic twin pairs), who ranged in age from 6-11 years old. In order to bridge the strengths of behavioral genetic methods and environmental assessment techniques, we used a multi-method, multi-measure approach to data collection, and analyzed the data using behavioral genetic modeling techniques. Results indicate that genetic variation accounts for a majority of the variance in parent reported child maladaptive behavior (average = 62%). Some parent report measures also suggest a smaller, significant contribution of shared environmental variance. In contrast to the parental ratings, the observational coding and global impressions of parent-twin interactive behavior suggest that shared environment is the primary source of variance accounting for parent and child maladaptive behavior. This is due, in part, to the direct influence that one’s interactive partner has on the expression of maladaptive behavior in an interactive setting. When the co-participant’s behavior is controlled for, genetic variation increases and shared environmental variation decreases.