The present area of distribution of New Zealand bats is considerably less than it was over a century ago. The decrease is correlated with the restriction of forest during the last century and the failure of either species to survive in open country or to urbanise. The Urewera in the North Island and the Buller River drainage in the South Island appear to support the highest densities of bats in New Zealand. Field observations in relation to behaviour and ecology are reviewed, and probable species differences in hibernation, foraging times, and diet are indicated. Fur mites are reported as parasites of both species.