Introduction The family life cycle indicates the developmental processes of family members (1). Duvall classified family cycle into the following stages: beginning families (I), families who are first time childbearing (II), those who have preschool children (III), families with school children (IV), those with teenagers (V), families with their first child gone to last child's leaving home (VI), and families who have in the middle years (VII) (2). Meanwhile, Rollins and Feldman also believed that the couples' relationships were influenced by different stages of the family life cycle (3). Marital satisfaction was defined as the happiness on different aspects of marital relationship (4,5). Lawrance and Byers defined sexual satisfaction as "an effective response arising from one's subjective evaluation of the positive and negative dimensions associated with one's sexual relationship" (4). Researches showed different patterns for marital satisfaction of the couples in the stages of family life cycle. For example, Lupri and Frideres obtained a U-shaped pattern which meant a decrease in marital satisfaction in the middle stages of life (5); however, Spanier et al reported curvilinear as well as negative linear trends; no relationship was found at all in three different samples between marital satisfaction and the stages of family life cycle (6). According to some studies, sexual relationship is an important factor in marital satisfaction of the couples (7, 8). People usually judge about sexual satisfaction based on their marital satisfaction (9). Besides, it is believed that the concept of sexual satisfaction is intricately intertwined with marital satisfaction (10). Despite the existence of different patterns between marital satisfaction and stages of family life cycle, there already exist a correlation between sexual and marital satisfaction regardless of the stages of family life cycle (7,8,10-15).In addition, sexual