AbstractThe factors related to the occurrence of extramarital coitus (EMC) among persons whose marriages terminate in separation or divorce and the impact of participation in EMC on postmarital adjustment were examined. It was hypothesized that premarital coital experience, quality of marital sex, length of marriage, religiosity, and physical attractiveness would affect the occurrence of EMC. Additionally, tests were performed to assess whether participation in EMC increased, decreased, or had no effect on postmarital adjustment. The data are from a study of 205 individuals, separated no longer than 26 months, who completed in‐depth, face‐to‐face interviews about their marriage, its failure, and its aftermath. Most respondents who experienced EMC report that it was an effect, rather than a cause, of marital problems. Yet respondents tend to report that theirspouse'sinfidelity was a cause of marital problems. Guilt is a significant by‐product of EMC for men and women, but men experience somewhat less guilt. Guilt is inversely related to satisfaction with EMC. Women report a significantly greater emotional involvement with their extramarital partners than men. Females who blamed their spouse or another person for the breakup of their marriage were significantly less likely to have had EMC, but no such relationship was found among males. Religiosity does not predict EMC, but among those who have had EMC, religiosity is positively related to how long after marriage EMC first occurred. There is no relationship between the presence or absence of EMC and marital quality at time of separation. Furthermore, EMC does not appear to be related to postmarital adjustment. Other variables such as marital quality, lifestyle attitudes, perceived consequences of EMC, perceived responsibility for family members, and perception of opportunity to engage in EMC need to be studied to further elucidate the occurrence of extramarital relationships.