Raspberries segregating for the Amphorophora idaei resistance gene, A10, were bioassayed and dichloromethane extracts from the leaf surface were examined by capillary gas chromatography. Thirteen compounds, present in all samples, were identified. They were straight chain hydrocarbons, acetic acid esters of long chain alcohols, tocopherols and triterpenoids. Several had not been recorded before in raspberry leaves. Linear discriminant analysis, applied to the standardized chromatographic data in an attempt to relate chemical composition to resistance, successfully partitioned 24 of the 26 plants into resistant and susceptible types as determined by bioassay. It is suggested that resistance in raspberry to A. idaei is related to the chemical composition of the leaf surface.