Numerous field studies have described male-male competition for mates across a wide range of species. Invariably large body size was correlated with high reproductive success. Many smaller males did not mate, and if they did, it was usually a result of employing alternative tactics, e.g., 'sneak' copulations, rather than via direct competition The purpose of the present study was to investigate the effects of male size and the state of female receptivity on the outcome of male-male competition in Nephila clavipes and to describe the competitive strategies employed by males. Contests between adult hub males of different body sizes were staged on both juvenile and sexually receptive female orbs. Procedures were instituted to ensure that all hub males used in the tests would defend their position and that transporting males from one orb to another did not radically affect their behavior. Females were observed for several days to ensure knowledge of their sexual receptive state. A daily census was taken after the staged encounters to determine the stability of male relationships Male tested against smaller opponents on juvenile female orbs employed an offensive strategy, regardless of whether they were the resident or visitor hub male. The strategies employed by males of equal size were more similar to one another than those of unequal size. Residents won 100% of the contests against smaller opponents, none of those against larger opponents, and 58% of the contests against opponents of equal size Resident hub males were competitively more successful when they were with sexually receptive females. This was due more to a shift in the strategy of residents than of visitors. Residents won 93% of the contests against opponents of equal size and 42% of the contests against larger opponents Measures of communication were calculated and compared for each group. Escalation and intensity of the conflicts were assessed. Costs and benefits were also estimated for the winners and losers