Samples from 90 vivax malaria-infected and 51 uninfected subjects from an endemic area of the Brazilian Amazon were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR–RFLP) to identify polymorphisms of the genes TNFA (−1031T > C, −308G > A, −238G > A), IFNG (+874T > A) and IL10 (−819C > T, −592C > A). The gene discussed is IFNG; the disease is Plasmodium vivax malaria.