This study offers prospective data on the psychological well-being of men and women before and after a marital separation, in comparison with a control group who remained married during the same period. Data were gathered as part of the Minnesota Family Health Study on a primarily middle-class White sample. Primary variables were current psychological well-being, self-esteem, mastery, substance use, and family income. Findings were quite different for men and women. Prior to separation, men in the disrupted group had lower psychological well-being scores than the continuously married group had, but showed no declines in any of the measures in the follow-up period. Separated women scored lower than did women from continuing marriages on psychological well-being prior to the separation, and they declined further afterwards. Separated women also increased their use of alcohol and other substances, and experienced a decline in family income. Findings are discussed in terms of the social causation hypothesis and the social selection hypothesis for understanding the relationship between divorce and mental health in adults. © 1989, SAGE PUBLICATIONS. All rights reserved.