The influence of green ants, Oecophylla smaragdina (Fabricius), on insect pests of cashew, Anacardium occidentale Linnaeus, in tropical northern Australia was investigated using field surveys and field observations. Oecophylla smaragdina was abundant in the native vegetation of the area, and it was a dominant predator when found in cashew plantations. Oecophylla smaragdina significantly reduced the numbers of the four most important species of insect pests (Helopeltis pernicialis Stonedahl, Malipatil & Houston, Penicillaria jocosatrix (Guenée), Amblypelta lutescens (Distant) and Anigraea ochrobasis Hampson) on cashew trees, and trees with higher numbers of O. smaragdina produced higher quality nuts than trees with fewer numbers of O. smaragdina. Other ant species also reduced pest numbers, but not as much as O. smaragdina. The possibility of using O. smaragdina to control insect pests of cashew in the future is discussed. © 1995, Cambridge University Press. All rights reserved.