Gay men in relationships are often overlooked in HIV prevention efforts, yet many engage in sexual behaviors that increase their HIV risk and some seroconvert as a result. While different aspects of gay male relationships have been studied, such as sexual agreements, relationship characteristics, and couple serostatus, little research combines these elements to examine HIV risk for this population. The present study recruited 566 gay male couples from the San Francisco Bay Area to study their sexual agreements, motivations behind making agreements, and other relationship characteristics, such as agreement investment, relationship satisfaction, intimacy, and communication. Participants rated their level of concurrence with a set of reasons for making their agreements. They were also measured on relationship characteristics using standard instruments. Analyses were conducted by agreement type (monogamous, open, and discrepant) and couple serostatus (concordant negative, concordant positive, and discordant). A majority reported explicitly discussing their agreements and nearly equal numbers reported being in monogamous and open relationships. A small number (8%) reported discrepant agreements. Across all agreement type and serostatus groups, HIV prevention as a motivator for agreements fell behind every motivator oriented toward relationship-based factors. Only concordant negative couples endorsed HIV and STD prevention among their top motivators for making an agreement. Mean scores on several relationship characteristics varied significantly. Couples with monogamous agreements had higher scores on most relationship characteristics, although there was no difference in relationship satisfaction between couples with monogamous and open agreements. Scores for concordant positive couples were distinctly lower compared to concordant negative and discordant couples. Agreements, the motivations behind them, and the relationship characteristics associated with them are an important part of gay male relationships. When examined by agreement type and couple serostatus, important differences emerge that must be taken into account to improve the effectiveness of future HIV prevention efforts with gay couples.