Total protein and protein fractions were determined in serum and milk samples collected from 60 dairy buffaloes suffering from clinical mastitis. Lactose, calcium, phosphorus, magnesium, potassium, sodium and chloride contents in milk samples were also detected. The results of this study showed that, during progressive mastitis, serum total pro­teins, albumin and B-globulins were significantly decreased, while, o. and a-globulins were increased. Milk protein was decreased when somatic cell count reached 2.22 ± 0.0045 million cell/m1 or more. Casein content was diminished and levels of whey proteins were increased as a conse­quence of mastitis. Although total casein percentage was dropped, the results diversed in fractions where a marked increase was observed in K casein fraction. The percentage of immunoglobulins and serum albumin in mastitic milk became several times higher in comparison with those in healthy buffaloes milk. The lactose level in mastitic milk was significantly reduced. sodi­um and chloride more concentrated in mastitic milk and the amounts of calcium, phosphorus, magnesium and potassium were decreased consid­erably. Generally, the quantity and quality of milk were greatly affected by the degree of udder inflammation which, in turn, affected the pro­cessing properties of milk and its nutritive value.