We report an evaluation of the immunostimulatory effect of propolis volatiles from a stingless honeybee. We studied 34 elderly residents at a special nursing home. Twenty-one subjects were treated with propolis, 8 with $Binchhat{o}$ charcoal and 5 subjects acted as controls. Subjects treated with either propolis or Bincho charcoal were housed in rooms separated from the other non-study residents in the nursing home. The effects of each treatment on natural killer (NK) cell activity and lymphocyte levels were examined after 2 months and then for a longer period. The results indicated that NK cell activity was significantly improved to that within the normal range only after propolis treatment.