Based on the Investment Model of Rusbult (1980), that explains why people stay in or quit their close relationship, the aim of this work was to find out whether there are sex differences in behavioral indicators of satisfaction, quality of alternatives, investments and commitment. Another aim of this study was to examine whether sex differences could be explained by normative gender role attitudes. It was expected that women would use behavioral indicators of commitment and satisfaction more frequently than men, men in contrast should use behavioral indicators of quality of alternatives and investments more frequently than women. The normative gender role attitudes should predict the frequency of use of behavioral indicators of the variables of the Investment Model. The data of behavioral indicators and the normative gender role attitudes were collected by means of an online-study. 102 heterosexual couples, aged from 18 to 47 years (M = 24.47) with an average relationship duration of 3.59 years, completed the questionnaire. The results indicate that women used behavioral indicators of quality of alternatives more frequently than men, whereas men used behavioral indicators of investments more frequently than women. No sex differences occurred with behavioral indicators of commitment or satisfaction. Women?s gender role attitudes significantly predicted women?s use of satisfaction and men?s use of commitment. Women used more behavioral indicators to express satisfaction, and men used more behavioral indicators to express commitment, the more traditional women were. Furthermore, the behavior to express investments was significantly predicted by the normative gender role attitudes of the partner. Women and men used more behavioral indicators to express investments, the more traditional their partners were.