Vitality of different industrial yeast strains was investigated using four standard fluorescent dyes by studying changes in microscopic evaluation of yeast nuclei and cell membranes. Fluorescent dyes were: acridine orange, DAPI, trypan blue and primuline. Comparison of the results obtained by fluorescent techniques with these dyes showed good correlation of yeast cell vitality measurements. Simultaneous staining with fluorochromes provides a powerful way to demonstrate culture heterogenity and changes within yeast cells during long cultivation.