The Syntex adjuvant formulation (SAF) is an effective adjuvant composed of a muramyl dipeptide derivative (threonyl-MDP) in an oil-in-water (o/w) emulsion vehicle. Threonyl-MDP (N-acetyl muramyl-L-threonyl-D-isoglutamine) was identified as a superior adjuvant to muramyl dipeptide (N-acetyl muramylL-alanyl-D-isoglutamine, MDP) demonstrating a lack of side effects (pyrogenicity, uveitis, adjuvant-induced arthritis) and increased adjuvant activity (1 –3 ). The SAF emulsion vehicle contains Pluronic? L121 (poloxamer 401) that has exhibited adjuvant activity in its own right (4 –7 ). Many investigators have utilized the SAF adjuvant with a variety of antigens such as influenza (8 ) and malaria (9 ). Whereas SAF has shown versatility with a variety of antigens (eliciting both cell-mediated and humoral immune responses), it may be most effective with antigens that are amphipathic (10 ). An amphipathic antigenwould be retained at the surface of the oil droplet through hydrogen bonding with pluronic (also retained at the surface of the oil droplet) and hydrophobic association between the hydrophobic region of the antigen with that of pluronic and squalane, the oil portion of the SAF emulsion. Antigen retention at the oil droplet may lead to an enhanced immune response through more efficient antigen presentation (3 ,10 ). SAF, or a suitable equivalent (see Note 1 ), provides an excellent tool for vaccine research.