We tested the ability of TiterMax adjuvant and a water-in-squalene emulsion containing P1005, a new synthetic nonionic block copolymer adjuvant, to serve as alternatives to the complete Freund's adjuvant (CFA) for induction of ovalbumin (OVA)-specific humoral and cell-mediated immune responses. Priming of OVA-specific antibody (Ab) production and cellular immune responses was investigated after subcutaneous (sc) immunization with OVA emulsified with these adjuvants in mice. OVA-TiterMax and OVA-P1005 stimulated Ab production that was comparable to that induced by OVA-CFA but with some differences in the kinetics of isotype expression. OVA-TiterMax and OVA-P1005 also primed helper T lymphocytes (Th) that produced interleukin-2 (IL-2) at levels equal to Th cells induced by OVA-CFA, when restimulated with exogenous OVA in vitro. All three adjuvants primed OVA-specific, CD8+, class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL). The ability of TiterMax and P1005 copolymer adjuvants to induce Ag-specific humoral and cellular (both Th and CTL) responses is generally comparable to CFA but with fewer undesired side effects than CFA. These results suggest that copolymer adjuvants are effective alternatives to CFA in many situations, especially for vaccine development. Because of its low toxicity, P1005 is a promising candidate adjuvant that may be useful in vaccines for humans.