Naturally occurring and selected pupal color phenotypes of Anopheles freeborni were found to vary in their susceptibility to 2 different strains of Plasmodium falciparum and 1 strain of P. vivax. With the Santa Lucia strain of P. falciparum from El Salvador, 4 naturally occurring pupal phenotypes were less susceptible to infection than the base colony. After selection, there were no differences between the different phenotypes and the base colony. Brown and green nonstriped forms were more susceptible than brown striped forms. When the selected lines were fed upon monkeys infected with the West African 1 strain of P. falciparum, all of the selected lines were more susceptible than the base colony. With the Salvador II strain of P. vivax, naturally occurring green nonstriped forms were less susceptible than brown striped and nonstriped forms. Upon selection, the advantage shifted to the green nonstriped and brown striped forms. A comparison with previous studies with An. albimanus indicated that the relationship between susceptibility to infection and pupal phenotype varied not only between the species of mosquito but between the two malaria parasites, P. vivax and P. falciparum.