To find whether green tea has anti-obesity effects in mice, female ICR mice were fed on diets containing 1, 2 and 4% green tea powder for 16 weeks and the body weight and food intake were weighed. After the administration of green tea, the ovaries, kidneys, adrenals, liver, spleen, brain, pituitary and intraperitoneal adipose tissues in the mice were weighed and lipid levels in the serum and in the liver and serum leptin levels were measured. It was found that body weight increase and intraperitoneal adipose tissues were remarkably suppressed by the administration of diets containing 2 and 4% green tea powder. Food intake was suppressed by feeding the 4% green tea diet. Concentrations of total cholesterol in the liver, triglycerides in serum and liver and nonestrified fatty acids in serum from mice which were administered green tea diet were lower than those in the controls. Leptin levels in serum showed a decrease with green tea treatments. These results indicated that lipid metabolism in mice was suppressed by the administration of green tea powder and thereby the fatty accumulation and body weight increase was suppressed.