The aim of this work was to study the influence of long-time continuous wine fermentation on yeast morphology. The process of fermentation was carried out in medium of high sugar concentration (about 320 g/dm3), for 3,5 months, at 22C in 4 columns fermentor (4 series). In this experiment, wine yeast Saccharomyces bayanus strain S.o./1AD from the Collection of Pure Cultures of the Department of Food Biotechnology and Microbiology of Warsaw Agriculture University was used. Yeast was immobilized on foam glass. In this study, before and after immobilization the cells were examined by light microscopy, scanning electron microscopy and computer image analysis. It was stated that yeast after 3,5 months of continuous fermentation was bigger and showed morphological and intracellular changes in comparison with cells before this process. Before immobilization yeast was ovoid, single or budding cells. Various shapes of cells were observed after immobilization: elongated, in the shape of ?pear?, very big round and ?pseudomycelia?. In ?pseudomycelium?, the cells remained firmly connected by their cell walls and cytoplasm. In some cells, degeneration of cytoplasmic content was observed, too. These cells contained ?granularity?. The results show that long-time, continuous fermentation in high sugar medium causes negative changes of yeast cells.