Although it is not certain when malaria began to appear in the Korean peninsula, it is believed to have had been an endemic disease until 1984. Vivax malaria reemerged in the Republic of Korea (ROK) in 1993. In the early period most of the cases occurred among soldiers stationed in the DMZ and the adjacent region. In order to cope with malaria, the soldiers at risk received chemoprophylaxis with chloroquine and primaquine. The regimen for the treatment of vivax malaria in Korea was established in 1950's. Primaquine was introduced in 1951, and the field testing during the Korean War demonstrated that the combination of three days of chloroquine administration with fourteen days of primaquine reliably prevented the recurrence of vivax malaria. The regimen has been used since then, but there were some controversies as to whether or not to start chloroquine and primaquine on the same day. Most of the current treatment guidelines recommend the use of primaquine for fourteen days to overlap with blood schizonticide agents such as chloroquine and routine tests for G-6-PD deficiency before use. Previous data showed that the G-6-PD deficiency rate has been found very low among Koreans. Thus, it is not always necessarily mandatory to test for G-6-PD deficiency among Korean patients.