Maternal depression in families having a child with a disability has been the subject of considerable research over the past 25 years. This review was designed to describe the literature on maternal depression, critique its research methodology, identify consensus findings across studies, and make recommendations for future research. A particular emphasis is on the distinction between exhibiting depressive symptoms and meeting clinical criteria for a depressive disorder, how or whether research studies made this distinction, and implications for our understanding of maternal adaptation to disability in a family member. Of the 42 articles reviewed, only eight were clinically diagnosed depression; most of them used a scale rating depressive symptoms. Across the studies, mothers of children with disabilities generally exhibited a higher than average rate of depressive symptoms and are more at risk for clinical depression, but the incidence may be lower than reported in previous literature. Child behavior problems, maternal stress, coping style, and support were consistently associated with depressive symptoms. We conclude that we know relatively little about clinical depression in mothers of children with disabilities. The distinction between clinical depression and depressive symptoms may be important in conceptualizing how a child with a disability can influence family members and the nature of support that may need to be provided. Future research should incorporate gold standard diagnostic tools and assess history, severity, and type of depression. Research is also needed to study treatments to reduce the occurrence of both depressive symptoms and clinical depression.