Twenty five cooking recipe with yam (Dioscorea japonica Thunb) have been developed and their hypoglycemic effects on diabetic patients were investigated. The results of the sensory evaluations revealed that the tested recipe were in good scores (overall acceptability scores 3.30-4.33) except Chojuli. The 10-panel members indicated that the yam cookings were more acceptable when they were cooked with other vegetables. Twenty seven diabetic patients were entered in a general hospital during the 2-month experimental period and they were allowed to consume the diet with yam cooking dish, 75 g of yam a day. The fasting blood glucose and 2-hour postprandial blood glucose levels were determined. The diabetic patients who consumed yam showed the lower blood glucose levels than those patients who were controlled with the hospital diet only. The hypoglycemic effects of the yam were more evident in the patients who were injected with insulin. The constant lowering effects of blood glucose levels were observed in the normal subjects who had taken the yam cookery, leading to that one subject who started with a low blood glucose level must stop the yam consumption after 10 days.