Levels of upper-body strength and power can distinguish between athletes of different levels in a number of sports. The purpose of this investigation was to compare the maximum upper-body strength and power of 22 professional National Rugby League (NRL) and 27 state- and city-league, college-aged (SRL) rugby league players. All players were from the same football club and had undergone the same preseason strength and power training program for the 8 weeks prior to testing. Maximum strength was assessed by a 1 repetition maximum bench press (1RM BP). Maximum power (Pmax) and power output with loads of 40, 50, 60, 70, and 80 kg (P40, P50, P60, P70, and P80) were assessed during BP throws using the plyometric power system (PPS). Despite no differences in body mass or height, the NRL players were significantly stronger and more powerful in every variable measured. Furthermore, the differences in power output between groups became more pronounced with increasing barbell loads. Overall strength and power were highly related (r = 0.82); however, the relationship between these variables was somewhat less in the stronger NRL, group (NRL, r = 0.58, SRL r = 0.85). The percentage 1RM which maximized power output was also significantly lower for the NRL group as well as for stronger subgroups within each group. The results suggest that maximum strength largely influences power output; however, once a strength plateau has been reached, the changing training emphasis toward power training or the negative effects of high-volume conditioning training may alter the extent of the relationship.