In 1989 through 1990, the authors conducted a cross-sectional survey of 1,437 homeless adults in northern California (98% response rate). Prevalence of alcohol abuse, illegal drug use, and psychiatric hospitalization when adults first became homeless were 15% to 33% lower than prevalence following homelessness. The largest differences between the homeless and a comparison group of 3,122 nonhomeless adults were for psychiatric hospitalization and alcohol abuse. However, when prehomeless prevalence of addictive and psychiatric disorders were compared with prevalence among the nonhomeless, absolute differences were not greater than 12%. Results suggest that the homeless are less deviant in terms of social, addictive, and psychiatric pathology than has previously been proposed. Findings illustrate the need to examine disorders antecedent to the loss of shelter and to present comparative data on nonhomeless populations (authors).