Total microbial protein synthesis rates in the rumen of buffaloes were estimated by isotope dilution technique, using 131I-albumin treated with tannic acid as a marker. The animals were fed groundnut cake treated with formaldehyde to meet 50% of their digestible crude protein (DCP) requirement and 2.5% urea molasses mixture was given to meet the remaining requirement of DCP. Wheat straw was fed as the basal roughage. The total average microbial protein synthesis was 58.14 g/day.