For 1 yr, monthly milk samples with varying SCC were obtained from 42 Holstein cows. Milk was analyzed for fat, protein, lactose, casein, and SCC and was used for laboratory scale cheese making. Cheese was assayed for fat, protein, total solids, and salt. Losses of milk components in the whey were also determined. Least squares analysis of data, which were adjusted for the effect of milk composition, indicated that levels of SCC in milk were negatively related to fat, protein, total solids, and fat in DM of cheese and positively related to protein in DM and moisture in nonfat substances. An increase of SCC from 100,000 to above 1,000,000/ml resulted in a cheese containing approximately 6.8, 3.6, 4.9, and 1.5% less fat, protein, total solids, and fat in DM, respectively and 4.4 and 2.0% more moisture in nonfat substances and protein in DM. Levels of SCC in milk were positively related to protein losses in the whey. Overall protein losses increased approximately 6.8% for the first million increase in SCC/ml. Regression analyses showed that cheese fat, total solids, fat in DM, and moisture in nonfat substances increased by 4.43, 1.92, 6.50, and 1.07%, respectively, while protein and protein in DM were decreased by 2.37 and 5.36%, respectively, for every percentage increase in milk fat. Cheese protein and protein in DM increased by 2.05 and 4.55%, respectively, while fat, total solids, and fat in DM decreased by 3.19, 1.25, and 4.13, respectively, per percentage increase in milk casein.