Implementing the method of determining pollen viability in sweet cherry is of importance both in assessing a pollinator in a varietal composition and in breeding work. Pollen viability in sweet cherries Van, Bigarreau, Burlat, Stella and Asenova Rana, flowering simultaneously with the new Yugoslav cv. Čarna, was tested as follows: pollen germination in vitro on agar-sucrose medium, pollen staining with fluorescein diacetate and pollen germination, i.e. pollen tube growth in vivo in the style of cv. Čarna by fluorescence microscopy. A certain degree of positive correlation was found to exist between in vitro and in vivo tests. Between the cultivars studied, potential pollinators, quantitative differences in the length and number of pollen tubes were found in the style of cv. Čarna with the in vivo test.