SUMMARY: The endogenous respiration of vegetative amoebae, harvested during active growth, was similar in both the culture medium and in the high salt medium used to induce the encystation of starved amoebae. The respiration of starved amoebae and early stages of encystation was suppressed in high salt medium and stimulated when returned to the culture medium. A transient increase in respiration was observed early in encystation, while the respiration of later encystation stages decreased to the low level observed in mature cysts.