 This is a randomized, open-label study that will treat adult subjects with Plasmodium vivax infection with chloroquine for 3 days and tinidazole for 5 days concomitantly to assess efficacy for radical cure clearance of blood and liver stages of infection. There will be randomization to a positive comparator arm treated with chloroquine and primaquine definitive radical cure in order to obtain an estimate of the rate of re-infection during the monitoring period in the study population. 