Dr. Robert K. Colwell, Professor of Ecology and Evolutionary Biology at the University of Connecticut, and the creator of "Biota: The Biodiversity Database Manager," provides this site, which contains full descriptions, free software for downloading, and a user's guide to "EstimateS," a statistical application designed for computing species richness (S) from sample data. Recently updated, EstimateS 5.0 "computes randomized species accumulation curves, statistical estimators of true species richness (S), and a statistical estimator of the true number of species shared between pairs of samples, based on species-by-sample (or sample-by-species) incidence or abundance matrices. For comparative purposes, EstimateS 5.0 also computes Fisher's alpha and the Shannon and Simpson diversity indexes for each sample, as well as the Morisita-Horn index of biotic similarity between samples." Information on downloading and using the program is provided at the site.