Wing and tail injuries and defects appeared commonly among members of pallid bat (Antrozous pallidus) colonies in southern Arizona. These injuries and defects can be grouped into the following categories: (1) membrane holes, ((2) bone abnormalities (nonsymmetrical forearm, curved forearm and fingers, protruding bones, broken fingers, and broken tails), ((3) missing membrane parts, and (4) embedded thorns and cactus spines. Some of these injuries and defects may be due to certain inherent problems occurring in conjunction with battype flight surfaces. The success of bats in spite of such disadvantages is perhaps due to: extra wing-load capacity, the ability to fuse broken or dislocated bones, the ability to heal rips and fill in membrane holes, a tolerance of asymmetry, and an ability to limit the continual danger of infection following membrane injury. INTRODUCTION AND METHODS During the summers of 1966 and 1967, as part of a continuing study of the natural history of the pallid bat (Antrozous pallidus), numerous individuals of several colonies located near St. David in southern Arizona were banded and repeatedly recovered. Each individual was weighed and measured, reproductive status was determined, and notes were taken concerning all physical abnormalities. Since many individuals were examined on several occasions, it was sometimes possible to, observe the early stages of injuries and to follow the progress of recovery. In some cases it was possible to estimate the effects that such abnormalities had on the bat. Most obvious was the common occurrence of injuries or other defects of the wings. For example, 28 individuals of a population of 63 (observed on 14 May 1966) had some type of wing defect. The defects ranged from minor and insignificant holes in the wing membrane to more serious conditions such as broken fingers or missing parts. Acknowledgments.-Field assistance for this study was furnished by Gary Bateman, George Lammers, Clay Mitchell, and Sterling Doster. Robert Baker provided special help in both the collection and interpretation of field data, and E. Lendell Cockrum in preparation of the manuscript. Partial financial assistance was provided by funds obtained from a National Science Foundation Institutional Grant administered by The University of Arizona.