Oral intake of specific probiotics has been reported to enhance the immunity of the elderly. Earlier studies have used milk or yoghurt as a probiotic carrier. We chose a commercial probiotic cheese to evaluate its potential as a probiotic food. Thirty-one healthy elderly volunteers (21 female, 10 male) aged from 72 to 103 (median 86) consumed a commercial probiotic cheese containing approximately 10(9) CFU day(-1) of Lactobacillus rhamnosus HN001 and Lactobacillus acidophilus NCFM. The 4-week probiotic intervention was preceded by a 2-week consumption of probiotic-free cheese (run-in) and followed by a 4-week wash-out period with the same control cheese. The cytotoxicity of peripheral blood mononuclear cells (PBMCs), the relative numbers of natural killer (NK) and NKT cells in the total PBMCs, and phagocytic activity were assessed. Consumption of the probiotic cheese significantly increased the cytotoxicity of NK cells. A significant increase in phagocytosis was observed for both the control and the probiotic cheese. Cheese was found to be an effective carrier for the study of probiotics, and daily consumption of the probiotic enhanced parameters of innate immunity in elderly volunteers. It remains to be determined whether this enhancement correlates with a beneficial effect on the health of the elderly population.