β1,3-glucans from fungi, cereals, seaweeds and bacteria have been shown to possess favourable biological and anti-carcinogenic activities including upregulation of phagocytosis, cytokine production enhancement, superoxide and nitrite production; antibody secretion and stimulation of signalling pathways associated with proto-oncogene expression. However, human dietary supplements containing β1,3-glucans vary in efficacy due to glucan source, the lifecycle stage of the source at extraction, extraction methods, purity, concentration and combination with other immunomodulators. A review of efficacy of some commercially available β1,3-glucan products is presented. Three apparently efficacious products in which β1,3-glucan was the only immunomodulator were identified: Glucan #300®, Maitake Gold 404® (diluted Yukiguni Maitake MD Fraction®) and Betamune®. A trial of Maitake Gold 404® produced evidence of standardisation problems. It is recommended that Yukiguni Maitake MD Fraction® (a more standardised alternative), Glucan #300® and Betamune® be comparatively trialled at optimal doses across immunological measures and tumor reduction. β1,3-glucans have been shown to be synergistic with conventional cancer therapies and monoclonal antibodies, as well as immunomodulators including vitamin C, transresveratrol, humic acids and Ashwagandha (Withania somnifera). Trialled commercially available products containing immunomodulator combinations have been shown to be inefficacious, apart from RVB300®, a β1,3-glucan/transresveratrol/vitamin C combination. The efficacies of various combinations of β1,3-glucans with other immunomodulators and the details of specific β1,3-glucan/monoclonal antibody synergies in treating particular cancer cell lines, require systematic elucidation.