Background: Primaquine (PRM), an 8-aminoquinolone, is the only widely used anti malarial that eradicates Plasmodium (P.). vivax and P. ovale hypnozoites to prevent malaria relapse. Objective: To evaluate the safety and effectiveness of PRM for prevention of P vivax or P. ovale malaria relapse in Japanese patients. Methods: This was a prospective, multicenter, open label, post marketing surveillance study in Japanese patients with P. vivax or P. ovale malaria without prior PRM exposure. Primaquine 30 mg or 0.5 mg/kg (up to 30 mg) was orally administered to adults and children, resp., for 14 days, per the package insert. Safety (during the 14-day treatment period) and effectiveness (prevention of relapse for 1 yr after the last PRM dose) were assessed. Results: Thirty-three patients were enrolled and received ≥ 1 dose of PRM and comprised the safety anal. set. Of these, 23 had ≥ 1 evaluation for malaria recurrence after their last PRM dose and comprised the effectiveness anal. set. Most(n = 24,72.7%) had P. vivax malaria, followed by P. ovale malaria(n = 9,27.3%). Two patients experienced 6 treatment-related adverse events, including blood creatinine increased, abdominal pain, abdominal pain upper, decreased appetite, nausea, and vomiting. No episode/s of malaria relapse occurred during follow-up (median [Q1, Q3] 379 [369,422] days). Conclusions: The safety profile of PRM in Japanese patients with P. vivax or P ovale malaria was consistent with the established profile of PRM. No unknown or critical safety concerns were identified. PRM was effective for the radical cure of P. vivax and P. ovale malaria.