In 1989 Guyana designated 3600km 2 of tropical rain forest as the 'Iwokrama Rain Forest Programme' (IRFP) for developing methods of sustainable forest utilization and for conserving biodiversity. Bat diversity was assessed in 5 km 2 of the IRFP area over a ten-week period. Effort totalled 22 400 m 2 mist-net hours during 26 nights, 227 m 2 harp-trap hours during 8 nights and 28 person days searching for roosts. This revealed 38 species of bats. In comparison with two other neotropical sites alpha diversity was high as shown by a Shannon diversity index of 1.30 for the 33 species taken in foraging areas by mist net and harp trap.Four forest types found here show some of the lowest floristic diversity in the neotropics. The high motility of bats allows them to exploit the range of forest types available locally, so avoiding constraints imposed within any one forest type.A list of bat species known from Guyana was compiled from the literature. A total of 96 species were found plus 17 unsupported records. The list is presented together with a further 45 species that potentially could occur. Our survey has shown that 45 of the 96 species recorded in Guyana (47%) are known from the IRFP area, suggesting that it provides a good representation of Guyana's bat fauna.