Four inmate volunteers were experimentally infected by sporozoite inoculation with the Chesson and Venezuelan strains of Plasmodium vivax and five inmate volunteers similarly infected with the B strain of Plasmodium cynomolgi. The course of malaria antibody production was followed using the indirect fluorescent antibody technique, and the production of γ-globulin determined by electrophoretic analysis of the volunteers serum proteins. The results of these studies have revealed the following observations. The prepatent period ends before malaria antibody is first demonstrated with a median difference of 6 days. The volunteers infected with P. vivax first demonstrated antibody between the 15th and 23rd days after infection. Maximum antibody titers of 1:320 to 1:5120 were reached 25 to 42 days after infection, and in two of the patients malaria antibody was still detectable 150 days after infection. Four of the five patients infected with the B strain of P. cynomolgi first demonstrated malaria antibody in their sera 17 to 24 days after infection. Maximum antibody titers of 1:320 to 1:5120 were reached 31 to 48 days after infection, and in two of the patients malaria antibody was still detectable 335 days after infection. All of the infected volunteers demonstrated an increase in their γ-globulin levels after infection. The maximum increase in γ-globulin varied between 0.20 to 1.80 grams per cent. The maximum antibody titer tended to occur at the same time as the maximum γ-globulin rise with a median difference of 3 days. These results suggest that the raised γ-globulin levels found in malaria infections correlate with the production of specific malaria antibody as determined by the fluorescent antibody technique, and that the humoral element of malaria immunity is part of the excess γ-globulin produced. The amount of malaria antibody present as γ-globulin is probably much less than the total amount of excess γ-globulin formed in response to infection with malaria parasites.