Both ethanol and water extracts of unossified velvet antler were found to exhibit a significant immuno-stimulating activity as measured by carbon clearance test in mice, a remarkable anti-fatigue effect in weight-loaded forced swimming performance in mice, a significant anti-stress effect on immobilization in rats. The antler extracts also showed a weak but significant anti-thrombotic activity. These findings are indicative of adaptogenic properties of antlers and their normalizing effects during stressful condition.