This invention provides methods to the determination of the viability of the
cell by a first reagent and the phenotype of a cell by use of one or more second
reagent. The first reagent is one that is detectable in viable, or living, cells
even after they have been fixed such that they are no longer viable. The one or
more second reagent is compatible for use in fluorescence activated cell sorting
(FACS) including intracellular FACS. The invention thus provides methods of simultaneously
identifying a cell as both viable and having a phenotype of interest. The invention
also provides compositions for use in the disclosed methods.