OBJECTIVE: To determine the sensitivity and specificity of the rapid diagnostic test OptiMAL for diagnosis of Plasmodium vivax malaria. MATERIAL AND METHODS: We included all the patients who sought medical attention in the San Martin Pangoa Hospital, Junin, an area endemic for vivax malaria in Peru, between October and December 1998, who had fever during the previous 72 hours and who were older than 12 months. The gold standard for diagnosis was thick blood film microscopy. We determined the parasitemia rate for each of the positive slides. We calculated sensitivity, specificity, positive predictive value and negative predictive value of the test. RESULTS: We included 72 patients; 39 of them were positive for P. vivax by microscopic examination. The sensitivity of the Optimal test was 92.3%, the specificity 100%, the positive predictive value 100% and the negative predictive value 91.6%. The accuracy of the test was 95.8%. The sensitivity of the OptiMAL test progressively decreased when parasitemia was lower than 1,000 parasites/microliter. CONCLUSIONS: the OptiMAL test has a high sensitivity and specificity for diagnosis of P. vivax malaria. However, its sensitivity decreased when parasitemia levels were lower. It is a very simple technique, which makes it a good alternative for malaria diagnosis in remote places, although its elevated cost is still a problem.