Prevalence of botfly (Cuterebra sp.) parasitism in populations of small mammals was studied in tallgrass prairie of northeastern Kansas during 1985-1987. Four species of rodents, Neotoma floridana, Peromyscus leucopus, P. maniculatus, and Reithrodontymys megalotis, were parasitized and all infestations occurred between 1 June and 30 September. Prevalence was greatest in July and August of all species. Proportions of N. floridana (0.31) and P. leucopus (0.24) parasitized were similar and significantly greater than those of P. maniculatus (0.08) and R. megalotis (0.02). Over 95% of the parasitized animals were adults with no differences noted due to sex. Parasitized individuals resided longer on the study area than unparasitized animals for N. floridana, P. leucopus and R. megalotis, but not P. maniculatus. The relationship between residence time and parasitism, as well as higher proportions of infestation for N. floridana and P. leucopus, probably due to overlap in preferred habitat (woody vegetation in ravines and contiguous lowlands) between adult Cuterebra and these rodents