This study was performed on two groups (10 cows) for primiparous Holstein lactating cows (av. 98 days in milk : DIM) which were divided into low forage diet (LF) and high forage diet (HF) groups based on forage : concentrate ratio (F : C ratio). The F : C ratios of LF and HF groups were 37:63 and 62:38, respectively. Concentrate intake was significantly higher in the LF group than the HF group whereas the HF group showed higher forage intake (12.9 kg) compared to the LF group (7.4 kg) (p<0.05). No significant difference was observed in total feed intake between the HF (20.9 kg) and LF (19.4 kg) group (p>0.05), but the HF group tended to be higher. CP, TDN and NEL intake showed no significant difference between the two groups (p>0.05). Though, there was no significant difference on actual milk between the two groups (26 vs. 23.9 kg/d, p>0.05), the LF group tended to be higher. 4% FCMs of LF and HF groups were 22.8 and 22.3 kg/d, respectively, and showed no significant difference (p>0.05). The HF group was higher in fat content and lower in MUN. C14:0, C16:0 and C16:1n7 of milk fatty acid were significantly higher in the HF group (p<0.05), but there were no differences in other milk fatty acids between the two groups. As a result, increasing high quality forage such as BIRG silage and hay in the diet will not only fulfill nutrient requirements but also reduce milk production. (Key words : Forage concentration, Feed intake, Milk, Composition, Fatty acid)