This study investigated whether satisfaction with open sexual agreements in gay men's relationships was associated with perceptions of discrepancies in the benefit experienced from those agreements. Three types of perceived discrepancy between the self and the relationship partner were examined: frequency of casual sex, attractiveness of casual partners, and "overall" benefit. Results from a survey conducted in 2010 of 685 Australian gay men in relationships with open agreements showed that men perceiving discrepancies in benefit, particularly those representing "under-benefit", were less satisfied with their agreement than were men perceiving equal benefit. These results supported hypotheses derived from equity theory and provide insight into factors associated with gay men's satisfaction with open agreements. These findings also have important practical implications. Professionals counselling gay men or couples experiencing low satisfaction with open agreements may consider raising issues of unequal benefit and work with their clients towards achieving equality.