This study examined the evolution of immunoglobulin (Ig) G1 and IgG3 antibodies against the asexual stage Plasmodium falciparum protein, MSP1(19), before and after a heavy malaria transmission period in clinically immune Senegalese subjects living under different epidemiological conditions. Plasma was tested for antibodies to a yeast-produced, recombinant PfMSP1(19) antigen (the Q-KNG allelic variant) that has previously been demonstrated to react with IgG1, IgG3, or both in the majority of these people. Anti-P. falciparum antibodies of the IgG1 and IgG3 subclasses, previously reported to be associated with protection, were shown to evolve independently one from another after the transmission period in both settings. These results suggest differential regulation of MSP1(19)-specific IgG1 and IgG3. The precise role of these antibody isotypes in maintaining malaria immunity remains to be determined.