To examine the anti-obesity effects of tea catechins in humans, a trial study using healthy male subjects(27-47 years). Comprising in equal number a low dose catechin(LDC) group(n=11) and high dose catechin(HDC) group(n=12). The groups were administered catechins at 118.5mg and 483.0mg a day for 12 weeks, respectively. At 4 and 12 weeks, effect evaluation was made based on change in weight, body mass index(BMI), waist circumference, body fat ratio and abdominal fat as determined by computed tomography(CT) and triacylglycerol, total cholesterol, free fatty acid, glucose, insulin and total plasminogen activator inhibitor-1(PAI-1) in serum. In the HDC group, at 12 weeks, weight, BMI, waist circumference, body fat ratio, abdominal fat and total cholesterol, glucose, insulin, PAI-1 in serum were noted to have significantly decreased from values at 0 week. In the LDC group, only weight, BMI and insulin had changed. In the HDC group, BMI had decreased significantly in 25.LEQ.BMI subjects compared to 25>BMI subjects. In the 25.LEQ.BMI subjects, BMI decreased significantly more in the HDC group. Tea catechins are thus shown here for the first time to have the anti-obesity effects in humans.