Commitment, in turn, is affected by three factors—satisfaction, investments, and the quality of alternatives. The investment model also predicts that individuals' feelings of commitment influence the stability of their relationship. In order to replicate and extend the generalizability of the investment model to married couples, this study tested the model in a large sample of married couples studied prospectively over an 18-month period. The relatively small percentage of variance in commitment accounted for by satisfaction, alternatives and investments may be attributed to restricted variance in some of our measures due to ceiling effects. Feelings of moral obligation are probably more relevant to married couples than to dating or even cohabiting couples. Among couples who completed the follow-up, these three variables together accounted for 16 percent of the variance in commitment for husbands and 22 percent for wives. Conceptual issues may also have limited our ability to predict couples' commitment to a relationship.