An water-in-oil (w/o) emulsion with immunomoadjuvant activity. Montanide ISA 51 VG appears to act by enhancing the immune system’s cytotoxic T-lymphocyte (CTL) response against antigen(s) in vaccines. The surfactant mannide monooleate in Montanide ISA 51 VG contains vegetable-grade (VG) oleic acid derived from olive oil.