The purpose of this study was to study the prevalence of having sex just to satisfy the partner (“duty sex”) in sub-groups of heterosexual couples with no, mild, and manifest reduced sexual desire, and to study the relationship between duty sex and interpersonal communication about sexual issues. The study comprises a representative sample of 398 couples aged 22 to 67 years. Data collection was carried out by self-administered postal questionnaires. The majority of the women (59%) and 28% of the men reported having duty sex. Two of three women and one of five men with manifest distressing reduced sexual desire had experienced having duty sex. The corresponding percentage among those with no desire problems was 39% and 24%, respectively. There was an association between duty sex and communication with the partner about what is sexually good for me, and about own sexual needs not being acknowledged, in women with mild reduced sexual desire. In men with manifest reduced sexual desire there was an association between duty sex and talking to the partner about what is good for me sexually, what one does not like sexually, and sexual fantasies. Thus, men with desire problems seem to communicate to their partner about their sexuality, whereas women seem not to talk to their partner about their sexual needs.