The ability to easily analyze apoptosis is important in studies of molecular cell biology and to evaluate the relative toxicity of different treatments or environments. This is particularly the case when substances such as morpholino oligonucleotides are injected into embryos, as such treatments can cause widespread, complex patterns of apoptosis. Zebrafish embryos are well suited for cell biological and environmental toxicity analyses, but the need remains for a simple method that can analyze levels of apoptosis in a statistically significant number of embryos. Here we present a "group fluorescence" method for rapid, large-scale analysis of relative levels of apoptosis based on densitometric techniques. ; Ben Tucker and Michael Lardelli ; Copyright © 2007 Mary Ann Liebert, Inc.