We investigated dietary effects of green tea powder (GTP) on plasma lipids, platelet aggregation, hemolysis, plasma TBARS, and liver enzymes. Thirty one volunteer diving women living on Jeju island consumed 4 g green tea powder daily for a period of four weeks and data for the study subjects were analyzed on the basis of diagnostic criteria for blood pressure (BP)(${geq}$ 140/90 mmHg), plasma total cholesterol (TC)(${geq}$ 200 mg/dL), and triglyceride (TG)(${geq}$ 150mg/dL). Subjects with high BP had significantly higher TC and TG than those with normal BP. Subjects with higher TC had higher TG, and those with higher TG had lower HDL cholesterol. Platelet aggregation in the initial slope was significantly higher in subjects with normal BP, normal TC, or normal TG than their counterparts in high BP, TC, and TG. HDL cholesterol after GTP intake increased only in subject groups with normal BP, normal TC, or normal TG, and plasma TG after GTP intake decreased only in groups with higher BP, higher TG, or higher TC. Plasma TC and TG in subjects with normal BP increased after GTP intake. GTP intake caused a decrease in the initial slope of platelet aggregation in all subject groups with little effect on maximum aggregation. Total bilirubin showed a significant increase and GOT increased in all subject groups after GTP intake. Beneficial effects of short term intake of green tea powder might differ depending on the subject conditions in terms of blood pressure, plasma lipids, and other cardiovascular conditions. However, with the hypolipidemic, antithrombotic, and antioxidant actions of its bioactive flavonoids, long term usage of GTP or brewed green tea may provide preventive effects against cardiovascular disease.