The immunogenicity of a malaria peptide presented in various forms was tested in terms of the quality and quantity of the antibody response in rabbits. Peptide conjugated to a protein carrier, diphtheria toxoid (DT), required strong adjuvants (e.g. muramyl dipeptide, MDP and Freund's adjuvant, FCA) to elicit high levels of antibody with high avidity. Alum was a poor adjuvant, producing the lowest titre and avidity of antibody compared with all the other groups. Peptide expressed in vaccinia (and without carrier) produced intermediate levels of antibody but the avidity of the antibodies produced were comparable to that produced by peptide conjugates given with muramyl dipeptide.