The ant fauna of a rain forest in Sabah, Malaysia was sampled by using different collecting methods in three strata. In total, 524 morphospecies of ants could be distinguished. They belong to seven subfamilies and 73 genera. So far, the ant community described is the most species rich published for a primary tropical rain forest. Regarding the stratification in the forest, the leaf litter community comprised as many ant species as the lower vegetation or canopy. Furthermore the litter stratum had the highest generic diversity. The stratification of ants in rain forests seems to be a very strict one with the majority of species (75%) being related to only one stratum. This is in contrast to findings on the stratification of beetles in rain forests. The stratification and a radiation of some groups into vegetation and canopy, where a broad spectrum of permanent habitats exist, is responsible for the high diversity of ants in tropical rain forests.