The fluorescein diacetate-ethidium bromide (FDA-EB) fluorescence method, primarily used to determine viability of mammalian cells, was applied to several fungi species. Living fungi cells produced fluorochromasia, i.e., an intracellular accumulation of fluorescein which could be easily visualized as a green color under the U.V. microscope. Dead cells showed a red bright color due to ethidium bromide penetration. The FDA-EB test can be successfully employed to assay yeast and yeast like cells viability since a good correlation was observed between this assay and the colony count technique. The main advantages of FDA-EB test are its speed, high sensitivity and simplicity.