elisa was evaluated for the serodiagnosis of plasmodium vivax using homologous antigen. this was a crude fraction obtained after detergent (np-40) lysis of human parasitized red blood cells. antibodies of the classes igm, igg, iga were determined in a pool of eleven sera from patients with p. vivax malaria. the protein a was introduced as secondary probe to screen p. vivax antibodies in 30 sera of patients harbouring a first episode of p. vivax malaria. there was a correlation of 93% with the parasitological diagnosis and the test resulted specific and reproducible.