It was shown that eight stages of transition are observed in the heating process of Spirulina platensis cells in temperature range 5-140degrees'C. The first stage covers the temperature range 5-53degreesC with maximum similar to45 degreesC. The heat evolved in this temperature range is equal to 380 20 J/g of dry biomass, it does not change at scanning rate lower than 0.083 degreesC/min and belongs, mainly, to cell respiration in a stationary regime, in the dark. It was shown that endotherm similar to66 degreesC belongs to denaturation of C-phycocyanin which denaturates in solutions with T-d = 64.2degreesC, DeltaH(d) = 34.7 +/- 2.1 J/g and for it is equal to 10.8 +/- 1.2. The endotherms with Td equal to 58 and 88 degreesC are connected with denaturation of phycobilisome proteins and endotherm with T-d = 48 degreesC and DeltaHd = 4.2J/g of dry biomass-with denaturation of protein which, apparently, is connected with cell respiration.