ELDA is a software application for limiting dilution analysis (LDA), with particular attention to the needs of stem cell assays. It is the first limiting dilution analysis software to provide meaningful confidence intervals for all LDA data sets, including those with 0% or 100% responses. Other features include a test of the adequacy of the single-hit hypothesis, tests for frequency differences between multiple data sets, and the ability to take advantage of cases where the number of cells in the sample is counted exactly. A webtool at http://bioinf.wehi.edu.au/software/elda/ provides an easy user interface.