Abstract The immuno-modulating properties of different adjuvant systems on the murine humoral and cellular immune response to a synthetic peptide comprising amino acid residues 9–21 of glycoprotein D of herpes simplex virus type 1 (HSV-1) were investigated. For immunization, the peptide was conjugated to ovalbumin or bovine serum albumin by glutaraldehyde and the adjuvants used in this study were Freund's complete adjuvant (FCA), aluminium hydroxide, the Ribi adjuvant system (RAS) and two non-ionic block polymer surfactants, viz. L101 and 31R1, in oil in water emulsions. High anti-peptide antibody titers were obtained after immunization with FCA, aluminium hydroxide, RAS and L101. All adjuvants, except RAS, stimulated the induction of delayed type hypersensitivity obtained after immunization with peptide 9–21 coupled to ovalbumin and elicited by injection of purified HSV-1 virions in the footpad. Challenge with a lethal dose of HSV-1 showed that mice immunized with peptide 9–21 coupled to ovalbumin in combination with FCA, RAS and L101, respectively, were significantly protected. Although immunization with peptide 9–21 coupled to ovalbumin combined with aluminium hydroxide stimulated induction of delayed type hypersensitivity, no significant protective immunity against the challenge was generated.