Polyclonal immune monkey serum raised against schizonts of Plasmodium knowlesi (H-strain) showed the presence of antibodies to lactate dehydrogenase (LDH) of P. knowlesi by immunodot enzyme staining method. The anti-LDH antibodies are most probably directed towards an epitope distinct from the catalytic site as shown by the specific enzyme staining of LDH after binding with antibody on nitrocellulose paper. These antibodies showed reactivity with LDH from different strains (H, P and W1 strains of P. knowlesi) and species (P. cynomolgi B, P. berghei, P. yoelii, P. falciparum and P. vivax) of malarial parasites but did not cross-react with three isoenzymic forms of mammalian LDH (A4, B4 and C4) as well as with LDH from some protozoan and helminth parasites. These findings suggest that the anti-LDH antibodies have defined specificity to Plasmodium spp.