Rusbult's (1980, 1983) investment model was utilized to explore the determinants of satisfaction with and commitment to maintain romantic relationships among male and female homosexuals and male and female heterosexuals. The study employed a questionnaire designed to obtain both specific and global measures of rewards, costs, alternatives, and investments, and to obtain global measures of satisfaction and commitment. Women, both lesbians and heterosexuals, reported that they had invested more in their relationships and were more committed to maintaining their relationships than did men. Heterosexuals, male and female, reported greater costs and marginally greater investments in their relationships. In general, the investment model effectively predicted satisfaction and commitment for the sample as a whole and for all four groups of respondents. Greater satisfaction with relationships was associated with higher levels of rewards and lower levels of costs. Greater commitment was associated with greater satisfaction, greater investments, and poorer quality alternatives. Relationship costs were more strongly related to satisfaction and commitment for females than for males. Differences in the average level and the importance of a wide variety of specific predictors were also examined. In general, gender appeared to be a more important predictor of the behaviors explored in this study than was sexual preference.