Rapid sexual involvement may have adverse long-term implications for relationship quality. This study examined the tempo of sexual intimacy and subsequent relationship quality in a sample of married and cohabiting men and women. Data come from the Marital and Relationship Survey, which provides information on nearly 600 low- to moderate-income couples living with minor children. Over one third of respondents became sexually involved within the first month of the relationship. Bivariate results suggested that delaying sexual involvement was associated with higher relationship quality across several dimensions. The multivariate results indicated that the speed of entry into sexual relationships was negatively associated with marital quality, but only among women. The association between relationship tempo and relationship quality was largely driven by cohabitation. Cohabiting may result in poorer quality relationship because rapid sexual involvement early in the romantic relationship is associated with entrance into shared living. (Contains 5 tables and 1 figure.)