The rose-grain aphid (RGA) is an introduced pest which attacks cereals and can cause considerable loss of yield. It is a pest of some economic concern in affected grain growing areas of New Zealand. In 1985 the DSIR introduced a parasitoid, Aphidius rhopalosiphi, in an effort to control RGA by biological means. This study aims to perform an economic evaluation of the biocontrol of RGA in New Zealand.