Heart mitochondria freshly isolated from ginseng treated rats respired higher at ADP-induced, state 3 respiratory rates and with greater respiratory indices. These mitochondria were less susceptible to experimentally-induced functional impairment. Control heart mitochondria incubated with ginseng extract also showed that ginseng prevented mitochondria from incubation induced deterioration with NAD-linked substrates. Comparison of force of contraction of isolated, perfused and electrically paced hearts showed that deterioration of the force of heart contraction was consistently smaller throughout the experiment in hearts from ginseng treated rats. These results indicated that Panax ginseng was able to delay experimentally induced heart mitochondrial impairment and muscle contraction deterioration.