Aspects of the intracellular energetic balance were studied in assimilating cells of Chlorella, grown in a medium with different concentrations of NaCl. The responses depending on salt concentration were revealed by a microcalorimetric method. The lower concentrations of NaCl (450 mM) induced an increase in the heat production by Chlorella. Under higher salt concentration (550 mM), a sharp increase in heat production took place. This was probably connected with the cell destruction. In explaining the results, the protective mechanisms of Chlorella connected with energy redistribution under different salt conditions, are emphasized.