The population dynamics of avian brood parasitism have received little attention in spite of mounting evidence that many host species are adversely affected by brood parasites. We develop models for the dynamics of brood parasitism and apply these models to host-parasite associations for which demographic data are available. For generalized brood parasites, which use many host species, we assume that the population dynamics of the parasite are unaffected by any one host species and that the hosts accept the eggs of parasites. The demographic consequences of parasitism for a population of a given host species can be estimated if one knows the probability of parasitism, juvenile and adult mortality rates, and the average number of offspring successfully fledged by parasitized and unparasitized females (eqs. 3, 4). Because these demographic data are difficult to obtain in the field, they are available for few species. Applications of this model using available data suggest that females of many parasitized sp...