The stagewise mortality, ovipositional biology, and egg viability of the cattle tick, Boophilus annulatus (Say), on nilgai antelope, Boselaphus tragocamelus Pallas, was compared with ticks reared on Bos taurus (Hereford) cattle. Mortality was highest during the larval stage on both host species, but larval mortality on nilgai (78.6%) was significantly higher than on cattle (45.6%) hosts. Mortality during the nymphal stage was also significantly higher on nilgai (49.3%) than on cattle (13.9%). During adult female development, although the mortality rate on nilgai was 40.9% compared with no mortality of females on cattle, this difference was not significant. Significantly fewer ticks reached repletion on nilgai (4.0 females per animal) than on cattle (48.5 females per animal). The mean female weight and egg mass weight of ticks obtained from cattle were significantly higher than ticks produced from nilgai. On the other hand, no differences in mean conversion efficiency index (CEI), preoviposition period, incubation period, or egg hatch were observed among ticks obtained from the two host animals. Although nilgai produce fewer replete females, and the females that do survive are smaller and produce smaller egg masses, nilgai cannot be disregarded in an eradication program. The fact that even a small number of viable ticks is able to reproduce successfully on nilgai could lead to the failure of current eradication strategies by compromising the required quarantine interval.