Glucans have a long history as nonspecific biological modulators. We compared the effects of three different glucans on immune reactions. Using two different administrations (intraperitoneal and oral) and two different animal models, we showed that yeast-derived Betamune (Biorigin, São Paulo, Brazil) caused significant stimulation of phagocytic activity as well as potentiation of synthesis and release of interleukin (IL)-1, IL-2, IL-4, IL-6, IL-8, IL-13, and tumor necrosis factor-alpha. In addition, Betamune inhibited growth of tumor cells in vivo and affected expression of several important genes in breast cancer cells. Compared to adult mice, young animals showed different sensitivity to glucan action.