Eighty-five samples of milk and Swiss cheese made from the same milk were collected at Cache Valley Dairy Association, Smithfield, Utah, between August, 1979, and July, 1980. The weights of the milk, Swiss cheese and the trim were carefully recorded. The milk samples were analyzed for fat and protein, and the cheese samples were analyzed for fat, protein and moisture. An attempt was made to predict Swiss cheese yields from the fat and protein content of the milk and the moisture content of the cheese. The data were analyzed statistically by Gauss-Newton non-linear least squares method of iteration. Three formulas for predicting Swiss cheese yield were derived. The differences among the three formulas in predicting actual yield were insignificant. A good comparison was demonstrated between Swiss cheese yield and fat and protein in milk. The effect of season on cheese yield was also evaluated. The highest yield of Swiss cheese was in December and the lowest yield was in July. This corresponded with high and low levels of fat and protein in the milk.