The activity levels of five defensive enzymes (peroxidase,POD; polyphenol oxidase,PPO; superoxide dismutase,SOD; L-phenylalanine ammo-nialyase,PAL; and catalase,CAT) were assessed in shoots of four commercial Eucalyptus clones (DH201-2,DH32-29,U6,GL9) at ages of 13,29 and 38 months.Levels were also assessed in healthy and damaged shoots of clone DH201-2 at 15 months,shortly after it was severely attacked by the shoot gall wasp Leptocybe invasa.Foliar levels of these five enzymes did not show any significant increases with age.The level of CAT was found to be significantly higher at ages 29 and 38 months in clone GL9,a clone relatively resistant to L.invasa,than in the three other clones whilst clone DH201-2,one relatively susceptible to L.invasa,had non-significantly lower levels than the other clones at all three ages examined.The levels of the other three enzymes showed no obvious differences between clones and overall activity levels of the five enzymes did not show any clear association with the qualitative ranking of the clones’ susceptibilities to L.invasa.In 15 month old trees of clone DH201-2 marked increases in the levels of CAT,SOD and PPO were observed in shoots attacked by L.invasa compared to shoots from healthy trees of the same age,whilst levels of PAL and POD decreased compared to those in shoots from the healthy trees.