Abstract: 82 and 145 patients of vivax malaria were treated with chloroquine alone (1,500mg for three days) and in combination with primaquine 22.5mg for 5 days respectively from October to November 1980 and followed up till July 1981 in Huanghuai Plain. The relapse rates were 45.1% and 15.2% and the average number of relapses of the patients were 1.4 and 1.1 respectively. All patients with more than one post-treatment relapse were children. No recrudescence within eight weeks was noted in either group. Most relapses occurred in May and June.The IFA test carried out in July 1981 revealed that the difference in the positive rates (≥1:80) .the total geometric mean reciprocal litres and the re-rising rates of antibody titre between the two groups were significant. These coincided with the parasitological relapse rates examined by microscopy simultaneously. It appears that IFA test may be useful in comparing the efficacy of different regimens in the treatment of tertian malaria.