The effects of multiple mating on fitness in the rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), were studied. In the first of a series of experiments, the impact of multiple mating on female fitness was determined by evaluating the effects of a single mating period with one male, continuous exposure to one male, and continuous exposure to five males. Continuous exposure to one male increased lifetime fecundity by extending the period of time progeny were produced compared with a single mating period with one male, although average progeny size was reduced. Exposure to five males significantly reduced female survival and the number and size of progeny produced compared with the other treatments. In the second experiment, the number of progeny and the length of time progeny could be produced from a single copulation were determined. Females became sperm depleted within 7 ± 1 wk after laying 259 ± 22 progeny, but a second mating period 9 wk after the first copulation extended progeny production. In the final experiment, the mechanism for the decline in progeny production at high male densities was determined to be reduced oviposition, caused at least in part by a high proportion of time spent in copula. The number of copulations has costs and benefits for females that may affect population dynamics.