Because there is limited information on CYP2D6 genotypes/predicted phenotypes from Cambodia, a country highly endemic for P. vivax, we retrospectively performed CYP2D6 genotyping on stored buffy coat samples from 96 volunteers who took part in two malaria studies in Oddor Meanchey Province, located in northern Cambodia, following re-consent for human DNA testing. Here, CYP2D6 is linked to malaria.