We tested whether the order in which males encounter females affects reproductive fitness in spotted salamanders (Ambystoma maculatum). Using mating chambers in the field, we allowed one male access to a female before a second male. We then used four microsatellite markers in paternity analyses of the resulting larvae. First males sired a significantly larger number of offspring than second males, suggesting that male reproductive success is greatly enhanced by early arrival at breeding ponds. Multiple paternity was common among clutches, and frequently larvae were assigned to unidentified males that had not been in the chambers. Sperm from these males had either been stored by females for a year or obtained more recently at other breeding sites.