The series of metabolic ward experiments, with 22 physically healthy men in each, covered dietary cholesterol intakes from 50 to 1450 mg. daily, with all other variables controlled. The serum-cholesterol data, plus the data from comparable experiments reported from 4 other institutions, were analyzed in regard to average serum cholesterol response (Δ Chol., mg./100 ml.) to changed cholesterol intake. Least-squares solution, using serum cholesterol responses in 19 sets of dietary cholesterol comparisons, gives Δ Chol. = 1.5(Z2 − Z1), where the subscripts refer to the diets compared and Z is the square-root of the dietary cholesterol, measured as mg./1000 Cal. The correlation between the average Δ Chol. predicted and that observed is r = 0.95. The serum response was the same over a wide range of dietary fat composition. Ordinary American diets range from about about 150 to 350 mg. cholesterol/1000 Cal. These extremes correspond to an average difference of about 9 mg. of cholesterol/100 ml. of serum if all other variables are constant. Change from 250 mg./l000 Cal. to a cholesterol-free diet will cause an average fall of about 24 mg./100 ml. of serum. But a 50 per cent decrease in dietary cholesterol will produce an average decrease in the serum of only about 7 mg./100 ml. For the purpose of controlling the serum level, dietary cholesterol should not be completely ignored but attention to this factor alone accomplishes little.