A new class of soluble phosphorylated glucans is described as well as the process for making the same. According to a preferred embodiment, the soluble phosphorylated glucan is derived from the yeast Saccharomyces cerevisiae. The soluble phosphorylated glucans are useful for prophylactic and therapeutic applications against neoplastic, bacteria, viral, fungal and parasitic diseases. Additionally, they may be administered as a non-toxic adjuvant, in combination with chemotherapy. The soluble phosphorylated glucans are also useful for stimulating macrophage cells, either in vivo or in vitro, to produce a cytotoxic/cyctostatic factor effective against cancer cells.