Insect pests cause injury to the rice plant in various ways. The brown planthopper sucks assimilates from the phloem (Sogawa 1982) and reduces plant height and organ dry weights (Rubia-Sanchez et al.2003). Mechanical injury is the removal of leaves or tillers using scissors. The manner by which injury is inflicted may vary, but the response of the rice plant to injury may be similar. Hence, it is important to compare the effects of BPH injury with that of mechanical injury to better understand plant response to BPH feeding. We chose two cultivars, Nipponbare, which belongs to japonica rice, and Taichung Native I (TN1), which belongs to indica rice, to determine if there is a difference between the two cultivars in plant response to injury.