The effect of imidazole antimycotics (clotrimazole, econazole, and miconazole) on mitochondrial functions were compared by the experiment with isolated rat liver mitochondria and it was found that their potencies in the uncoupling effect on oxidative phosphorylation, in the stimulation of latent ATPase activity, and in the induction of swelling in mitochondria were enhanced by the increased chlorination of the molecule, i.e. miconazole greater than econazole greater than clotrimazole.