A feeding experiment was conducted for 2 months to evaluate the nutritive value of either fermented or alkali treated rice straw for lactating dairy cattle. Twelve mature Holstein cows were divided into 3 groups according to their age, body weight and previous production record. They were, then randomly assigned to one of three treatments. Three treatments consisted of control, fermented and, alkali treaty group. The control diet was 100% formula feed while the experimental diets were consisted of 85% formula feed plus either of 15% fermented or alkali treated rice straw on the dry weight basis. All animals were fed identical roughages according to NRC standard. The results obtained were as follows: 1. Average daily milk production for control, fermented and alkali straw groups were 15.8, 16.0 and 16.1 ㎏, respectively. 2. Feed costs per ㎏ of milk produced were estimated to be 40.1 won for the control, 38.7 won for the fermented and 36.8 won for the alkali treated straw group. These differences were not statistically significant.