The oxygen consumption of fresh and aged slices of potato tuber was 40.6 and 168.0 ,$0_2$ $mu$l/g fr $wt{cdot}h$, respectively. After initial burst of oxygen consumption within 2 minutes(i.e., 40% for fresh and 12% for aged slices) in the treatmentof $50{mu}M$ alantolactone, gradual decrease of respiration rate was observed during 3 hours of incubation. In case of the aged slices the initial burst of oxygen consumption was not observed by salicylhydroxamic acid (SHAM) or KCN. The combined effect of SHAM and alantolactone showed increase of 12%, while SHAM and KCN combination showed 60% decrease. In addition, the lipophilicity of cell membrane of onion inner epidermis was increased by lantolactone treatment. The results suggest that the primary effect of alantolactone on the cellular respiration may be associated with an alteration of lipophilic phase of cell membrane and a consequent increase of electron flow throuh the cytochrome system.