Adjuvant formulations which elicit both humoral and cell-mediated immunity will be required for vaccines based on peptides, viral and bacterial subunits and genetically engineered antigens. This report describes an adjuvant formulation which increases both cell-mediated and humoral immunity and is free of significant side effects encountered with other adjuvants or vehicles. The components include the threonyl analogue of muramyl dipeptide, Tween 80, Pluronic L121 and squalane. This formulation was found to be effective with several antigens, in several species, including rodents, cats and monkeys. These results suggest that the formulation will be useful for both human and veterinary vaccines.