Great public health benefits are gained by targeting the sexual forms of Plasmodium falciparum, – the gametocytes – since this is the form of the parasite that gets transmitted to other susceptible hosts via the mosquito. While Artemisinin-based Combination Therapies (ACTs) do have some gametocytocidal activity, only the 8-aminoquinoline (8-AQ) class of anti-malarial compounds (such as primaquine) have demonstrated the ability to target the key form of gametocyte that eventually gets transmitted – the stage V. The efficacy of primaquine is dependent on the ability of the human body to metabolize the drug into its active metabolites, a process that is thought to be mediated by the cytochrome P450 system. Unfortunately, the use of 8-AQs is limited by their tendency to cause haemolytic anaemia in individuals with a genetic deficiency in glucose-6- phosphate dehydrogenase (G6PD). This study proposes to estimate the prevalence of G6PD deficiency and also to study primaquine metabolism and its association with the alleles of the CYP2D6 and CYP2C19 genes among the population of Seme and Kisumu West sub-counties of Kisumu county, western Kenya.  The findings of the study will likely influence policy regarding the use of primaquine within the region.