This article discusses the effects of cohabitation and marriage on binge drinking, cigarette smoking and marijuana use in the U.S. The authors argue that marriage causes reductions in risky behaviors like binge drinking and marijuana use (especially for men), but has little effect on smoking. Less consistent are the effects of cohabitation on risky behaviors. Both marriage and cohabitation appear to reduce binge drinking for women, whereas women’s marijuana use is not impacted. They conclude that the beneficial impacts of marriage on drug use appear equally strong for blacks and whites.