Bulletin Volume 230. Paperback in original blue wrappers, faded spine. Information about the magnitude and geographic distribution of mammalian diversity in Neotropical lowland rainforests is important for evaluating research and conservation priorities in Central and South America. Although relevant inventory data are rapidly accumulating in the literature, real site-to-site diversity differences are hard to identify because many confounding factors can affect the size and composition of faunal lists. Herein the authorís assessed the available information about Neotropical rainforest mammal diversity and suggest guidelines for future work by reviewing inventory methods, documenting and discussing faunal lists from ten localities, and summarizing geographic range data to predict diversity patterns that can be tested by field and museum research.