Penicillaria jocosatrixGuenée consumes new leaves, flowers, and fruits of mango and has been a serious pest on Guam. Before 1986, few natural enemies were present and there were no parasitoids attacking the larvae. In 1986, a program was initiated to introduce larval parasitoids. The waspsAleiodessp. andEuplectrussp. and thefly Blepharella lateralisMacquart were released.Aleiodessp. did not establish, butEuplectrussp. andB. lateralisdid. Populations of the mango shoot caterpillar fell to 25% of their prerelease levels. Parasitization rates ranged from 20 to 99%.Euplectrussp. was the most abundant parasitoid. It parasitized all instars, but was more common on second and third instars. More eggs were laid on older instars of the caterpillar.Euplectrussp. was more abundant in the dry season whereasB. lateraliswas more common in the wet season. Fruit production on monitored trees increased significantly after the parasitoids became effective.