Research investigating patterns of familial aggregation of psychiatric disorders has used the family history method in which a single family member reports on the psychiatric history of their relatives. This method is more efficient and less costly than the family study method, in which direct interviews are performed on as many family members as possible. The family history method has been shown to have good specificity, in family studies of depression, but sensitivity has been less acceptable. The present study is the first study to report on the sensitivity and specificity of five psychiatric diagnoses made in a substance abusing population using the family history method. Among substance abusers and their family members, substance abuse is the most accurately diagnosed disorder. However, among family members only, the accuracy of diagnosing substance abuse declines significantly. Spouses and offspring are better informants than parents or siblings, and female relatives are better informants than male relatives. When more than one informant is available and positive diagnoses are determined by any positive family report, sensitivity for most disorders increases significantly. The results are discussed in terms of increasing the accuracy of the family history method.