Neutral red and Nile blue were found to be suitable for staining protoplasts from various strains of Saccharomyces cerevisiae. The absorption of stains by the protoplasts was dependent on the pH value, for both stains. At a pH of 7.9 the protoplasts of the fusion partners could be stained differently and therefore it was possible to observe the fusion between the various strains of yeast. Consequently the prerequisites were created for the following micromanipulation.