AbstractThe dynamics of bovine tuberculosis infection in a wild Badger population have been studied since 1981. Faeces are sampled regularly to determine the distribution of infection in the study area. Badgers in known infected social groups, plus the neighbouring groups, are periodically caught and subjected to full clinical and bacteriological examination to monitor the progression of infection within and between groups of Badgers. The interim results of this study are presented and discussed. During 5 years (1981–1985), the temporal spread of infection between social groups in the study area was slow and restricted. Some clinically affected Badgers have survived for long periods. Evidence of infection in individual Badgers indicates that pseudo‐vertical (mother to cub) transmission may be important in the maintenance of infection in the Badger population. There is also evidence of horizontal transmission by bite wounding and aerosol infection. Badger mortality due toMycobacterium bovisinfection was low, and the prevalence of infection in male Badgers is greater than in females. The data accumulated so far show no apparent relationship between Badger population density and the prevalence ofM. bovisinfection, nor is there any evidence to support the hypothesis thatM. bovisinfection acts to depress Badger population density significantly below disease‐free levels. Cattle and infected Badgers can co‐exist for long periods without the disease necessarily being transmitted to