Effect of live yeast culture (Saccharomyces cerevisiae plus growth medium) inclusion in the diet of buffaloes (Bubalus bubalis) on milk yield and its composition was examined. Twenty buffaloes (Murrah breed) having an average daily milk yield of 8 to 10 I and in their early lactation stage were divided into two equal groups. The control group was given a basal production diet consisting of 35 to 40 kg green berseem and concentrate mixture (0·5 kg/kg milk produced) per day per animal and the yeast supplemented group the above diet supplemented with 10 g yeast culture (YC, 5 × 109 c.f.u. Saccharomyces cerevisiae strain 1026 per g). The feeding continued for 10 weeks and during this period milk samples collected at weekly intervals and milk yield recorded daily. During this period, average daily milk yield was increased by proportionately 0·135 and fat-corrected milk yield by 0·185 by inclusion of YC. Fat, protein, lactose and total solids in milk increased proportionately by 0·039, 0·051, 0·030 and 0·034 respectively. The corresponding proportional increases in the quantity of these constituents secreted in milk (kg/day) were 0·237, 0·200, 0·200 and 0·204.