This study examined mothers' attributions of the causality of noncompliance in their children with Down syndrome (n = 37) compared with children with other causes of mental retardation (n = 22). Mothers rated two vignettes of simple noncompliance and completed questionnaires about their child's personality and maladaptive behaviors. Instead of attributing causality along the "classical" categories of locus, controllability, and stability, mothers in both groups used normalizing-temporary and excuse-making attributions. Higher ratings of normalizing-temporary compared with excuse-making occurred in both groups. There was also an interaction effect such that, compared with mothers in the mixed group, mothers in the Down syndrome group showed higher normalizing-temporary versus excuse-making attributions. In the Down syndrome group, normalizing-temporary attributions correlated negatively with children's internalizing behaviors and positively with children's personality. Excuse-making attributions correlated with children's externalizing behaviors in the Down syndrome group and with children's internalizing problems in the mixed group. Our results highlight the importance of understanding parental attributions for noncompliant behavior among children with different causes of mental retardation.