The reproductive biology and the population structure ofBandicota bengalensiswas studied from a regular monthly collection, made in the Paddy fields around Bangalore, Karnataka from 1982 to 1984. The bandicoot exhibits a seasonal reproductive activity lasting from early August till the end of April with an anoestrous period between March and July. Correlatively, the reproductive glands and the sex accessories show seasonal changes in their weights. The peak reproductive activity was seen during September, October and November, when the prevalence of pregnancy was 0.81 with a mean litter size of 7.1. Analysis of data compared with temperature and rainfall showed that variation in breeding activity could be due to rainfall and the availability of food in the environment. The annual reproductive rate is calculated to be 67 young per female per breeding season. The bandicoots exhibit lesser body weights during summer months, and greater body weight coincides with the peak breeding season when the paddy crop is maturing. It is suggested that May, June and July are the best months for the initiation of control measures against this major rodent pest species, when their populations are at a minimum (reproductively inactive) to achieve economic and effective results.