Research indicates that relatives of individuals with autism have higher rates of affective disorders than both the general population and families of children with other developmental disabilities. In addition, individuals with autism have high rates of co-morbid mood and anxiety disorders. This study sought to identify possible reasons for these previous findings by documenting the presence of affective disorders in both probands (the individuals with autism) and their family members. A sub-sample of 17 adults with autism and their first-degree relatives from the Baltimore Family Study of Autism completed a structured psychiatric interview. The results indicated that the rates of mood and anxiety disorders were 35 and 77%, respectively, for probands, and these disorders were present in at least one first-degree relative at rates of 71 and 29%, respectively. Exploring patterns within families revealed that 80% of probands with a mother who had a mood disorder history also had a mood disorder themselves, compared to only 16% of probands whose mothers did not have a mood disorder history. The results must be considered preliminary given the small sample size. Replicating these findings in a larger sample would help clarify whether a true increased risk of mood disorder exists, which would have potential implications for prevention efforts and understanding possible genetic mechanisms.