Blood biochemical studies were performed on 21 azotemic cattle with various disease conditions. The cattle were greater than or equal to 4 months old. Blood urea nitrogen concentrations ranged from 41 to 346 mg/dl. The azotemia was determined to be of prerenal origin in 10 cattle and of renal or postrenal origin in 11 cattle. The most consistent biochemical finding was that of hypochloremia. Sixteen cattle had lower than normal concentrations of serum calcium, and 15 had serum inorganic phosphorus concentrations greater than normal. In 17 cattle, the serum concentration of inorganic phosphorus was greater than that of calcium. Plasma sodium content was lower than normal in 9 of the 21 cattle, and plasma potassium concentrations were quite variable. Most of the cattle tended to maintain a normal acid-base status or had metabolic alkalosis. It was concluded that evaluation of biochemical data does not make it possible to determine whether azotemia is prerenal, renal, or postrenal in origin.