Malaria vaccines are developed to neutralize the antigen or to block the development of subsequent stages. The kinetics of antibody binding is considered in functional tests, such as agglutination, complement activation, inhibition of invasion and transmission blockade. Antibody-binding rate (and thus concentration) appears more important for antigen complexing than affinity. In vitro assays have to be carried out under conditions that approach the situation in vivo to avoid an overestimation of protective potential. The concentration of monoclonal antibodies applied in in vitro assays may differ totally from that of naturally occurring antibodies to the some surface epitope. Estimation of concentration rather than titre provides an appropriate measure of the vaccine-induced antibody response. [This important point of view deserves close attention of all those who study the protective effects of vaccine trials and of naturally occurring antibodies. It would be worthwhile to enrich the literature further with practical examples of kinetic studies in which in vitro models are matched with reality.]newline˜J.P. VerhaveADDITIONAL ABSTRACT:The kinetics of antibody binding is discussed with regard to invasive stages and the blocking of target recognition molecules, agglutination of merozoites, and complement activation. Investigations of antibody inhibition mechanisms are briefly reviewed. It is concluded that where the binding of antibody is likely to be kinetically constrained, the best vaccination procedure will be the method which gives antibody with the greatest rate of binding rather than the highest avidity.