The definitions of psychrophilia and psychrotolerance are based on the optimal temperature of growth (≤15 and 20 °C, respectively), and it is not clear whether differences exist in adaptation mechanisms. We analyzed the composition of osmolytes and membrane lipids of a true psychrophile Mucor psychrophilus during submerged cultivation at 12.5 °C and 4 °C, as well as under heat and osmotic shocks. The main osmolyte at 12.5 °C is trehalose (70 % of the total), whereas at 4 °C, comparable proportions of glycerol, glucose, and trehalose are observed. Under heat shock, the amount of trehalose increases threefold, and osmotic shock leads to an increase of the glycerol level without a reduction in the amount of trehalose. The predominant membrane lipids at both temperatures are non-bilayer phosphatidic acids (about 65 % of the sum) and phosphatidylethanolamines (20-30 %). An increase in the degree of unsaturation and a decrease in the sterols proportion are observed during growth at 4 °C, whereas at 12.5 °C, as well as under heat and osmotic shocks, the changes are insignificant. Similarity of the adaptation mechanisms of the psychrophilic and psychrotolerant fungi indicates the ambiguity of psychrophilia and psychrotolerance definitions.