Seven Anopheles species/isolates were compared with Anopheles dirus (control) for susceptibility to Plasmodium cynomolgi B strain. The mean numbers of oocysts in paired replicates of An. dirus and An. takasagoensis were not significantly different. The remaining test species had significantly fewer mean numbers of oocysts than Anopheles dirus (P less than 0.01). Anopheles dirus had the highest percentage of mosquitoes infected with P. cynomolgi sporozoites (82%). Of the test groups, Anopheles dirus B and An. takasagoensis had the highest percentage of mosquitoes with sporozoites, 77 and 78%, respectively. Fewer than 50% of Anopheles maculatus E and An. maculatus B (NN isolate) had sporozoites in the salivary glands. Anopheles maculatus B (HK isolate) and Anopheles philippinensis were the least susceptible, with fewer than 30% having sporozoites in the salivary glands.