During fermentation of classical (12%), HG (15%) and VHG wort (18%) physiological state of brewing yeasts (Safale US-05 and Safbrew T-58) was observed. After innoculation and during selected moments of wort fermentation the following features were examined: biomass concentration, yeast cell size, contribution of budding cells, magnesium ion concentration. The Safale US-05 beter adapted to the high concentration of wort. These yeasts produced more biomass, budded for a longer time of fermentation and maintained the cell size on the constant level. The secretion of magnesium ions into the wort in the beginning of fermentation showed also the good condition of these yeasts.

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