The relationships between maternal history of depressive symptoms during children's middle childhood (8-11 years) and/or concurrent maternal depressive symptoms on the one hand and teacher and self reports of conduct disorder and attention deficit behaviours when the children were 12 and 13 years old on the other were studied in a birth cohort of New Zealand children. Examination of the joint effects of maternal history of depression and concurrent depressive symptoms on child behavior showed consistent and statistically significant associations between maternal history of depression and behaviour reports. However, associations between maternal concurrent depressive symptoms and child behaviour were generally non-significant when the effects of maternal history of depression were controlled. These results persisted when errors of measurement in behaviour reports were taken into account. However, after adjustment for potentially confounding social and contextual factors the correlations between maternal history of depression and child behaviour reduced to the point of both practical and statistical non-significance. We concluded that, for this cohort, the association between maternal depressive symptoms and externalising behaviour in early adolescence arose largely from the effects of common contextual factors (principally social disadvantage and marital instability) that influenced both rates of maternal symptomatology and rates of childhood problem behaviours.