Blood serum samples were obtained from 114 crossbred calves on a feed trial under feedlot conditions at the end of a 56-day feeding period. Average values for 19 blood components were determined. The effects of the 3 trial rations and 2 electrolyte treatments were analyzed. Except for inorganic phosphates, urea nitrogen, cholesterol, glucose, alanine aminotransferase, and alkaline phosphatase most mean values were similar to those in dairy cattle. Urea nitrogen values differed significantly (P less than 0.05) in animals fed different rations apparently reflecting the crude protein content of each ration. The mean values presented can be used as base-line data for comparison with other similar studies or with values from diseased animals.