Darwin noted that many animals (usually males) have traits that are unlikely to have been favored by natural selection, as they appear to have a negative effect on an individual's ability to survive. He hypothesized that such traits might be due to sexual selection, enhancing reproductive success rather than survival. Sexual selection would favor traits that give individuals an advantage in direct competition with rivals (intrasexual selection), or that the opposite sex found attractive (intersexual selection for epigamic traits). Antlers in deer appear to exemplify the former: males grow them before the breeding season, engage in ritualized combat with other males, and shed them in the nonbreeding season. Peacock tail feathers, which are believed to attract females, are not shed seasonally. The distinction between intersexual and intrasexual selection gets blurred at times when it is argued that males compete with each other to be more attractive to females, or that sequestering females is a response to male competition or a variation on the theme of attracting females (by force in this case). Further, it is argued that females may select certain males because the male's genetic contributions would enable their sons to defeat rivals or attract females. It is also sometimes argued that females select mates that have a greater ability to survive, as demonstrated by their survival despite elaborate handicapping ornaments. (However, males that evolve the largest handicap that they can offset by their good traits are ultimately no better genetic sources than the less handicapped males.) This is Volume III of Special Topics in Primatology. Dr. Jones selected the authors who contributed; however, the authors did not meet to hear each other's papers and discuss their views. Drs. Jones and Nunn (who wrote the final summary chapter) did read all of the chapters, but in only three other cases was there evidence that the contributors were aware of the other papers. All of the authors were asked to write about sexual selection in primates, but apparently they do not all classify the various expressions of sexual selection in the same way. They all seem to agree that both males and females may compete for mates, and that both sexes may exercise choice, although it is often difficult to decide whether a particular observation is due to male or female choice, or whether the ''choice'' was imposed by members of the opposite sex. Some of the authors present and