The effect of replacing of 20;of cottonseed-cake by that of rubber seed cake in the concentrate mixture of 8 Jersey x Tharparkar cows on its milk yield and composition was studied. The cows were fed fodder maize (Zea mays) and concentrate mixture to meet their requirement of maintenance and production. There was no significant difference in their DMI, DCPI and TDNI/unit metabolic weight. The DCP and TDN contents of the ration fed to control group were 8.09 and 63.39;, while in experimental group these were 9.12 and 61.4;respectively. Average milk yields in cows of control and experimental groups were 8.77 and 9.96 kg respectively. The ME utilized by the cows/kg FCM in control and experimental groups were 1.21 and 1.23 Mcal respectively. The feed costs to produce 1 kg milk in control and experimental groups were Re 0.68 and Re 0.65 respectively. The study indicated that rubberseed-cake can safely replace cottonseed-cake in the concentrate mixture without affecting milk yield.