The authors used latent class analysis to investigate rules guiding nonmonogamy in partnered gay and bisexual men. Data are from a 2010 survey (N = 463) from which those in relationships (n = 191) were analyzed. More than half (56%) were nonmonogamous, and these men responded to 13 rules about sex outside of their relationship. The safe anonymous sex group (34%) included men who indicated that they must use condoms for anal sex and not have sex with people they know. The communication mandate group (19%) included men who indicated that they must talk about outside partners before sex occurs, disclose their relationship status to outside partners, and use condoms for anal sex. The play together group (9%) included men who indicated that they must play with others as a couple, not have anal sex with outside partners, and not spend the night with outside partners. Those in the no salient rule group (37%) were individuals who did not endorse a clear set of rules. These 4 groups (and compared with monogamous men) differed in age, agreement formality and flexibility, relationship satisfaction, and whether anal sex recently occurred with casual partners. This study provides a novel approach for understanding nonmonogamous same-sex relationships and highlights their complexity.