Rice (Oryza sativa L.) plants were grown over a 30-d period in nutricnt soiution containing concentrations of Cu varying from 0.002 to 6.25 g iit^, and ihen oxygen toxicity was investigated in the chloroplasts. The Cu concentration in the shoots increased with increasing levels of this metal in the nutrient soiution, whereas the Fe concentration decreased after the 0.05 g m'^ Cu treatment and the Zn concentration did not show any clear tiend. Catalase, glutathione reductase and Cu,Zn-superoxide dismutase activities decreased with increasing Cu levels. On a fresh mass basis, ethylene production decreased after the 0.05 g Cu treatment, whereas, on a chlorophyll (Chl) basis, it increased until the 1.25 g m‘^ Cu iTeatment. The chloroplast lipid peroxidation increased (on a Chl and lipid basis) between the 0.01 and the 1.25 g m"^ Cu treatment. On a fresh mass basis the concentration of chloroplastic digalactosyldiacylglycerol, monogalactosyldiacylglycerol, phospha- tidylcholine, phosphatidylglycerol and phosphatidylinositol decreased, whereas, on a Chl basis, the concentration of the first two lipids sharply decreased after the 0.01 gm‘3 Cu treatment. Additionally, only a slight decrease was foiind in the concentration of phosphatidylglycerol with increasing Cu concentrations. Measurements of the linolenate hydroperoxide concentration in these acyl lipids showed an increase after the 0.01 g m'^ Cu treatment for the fnst two lipids as weil as an increase with increasing Cu levels for phosphatidylglycerol.