Objective To evaluate the effect of a single dose of recombinant bovine somatotropin (bST) on certain metabolic values, health, and milk production of dairy cows undergoing surgery for left displacement of the abomasum. Design Blinded clinical trial. Animals 413 cows with left displacement of the abomasum. Procedure A single 500-mg dose of bST was administered to dairy cows following surgery in field practice conditions for left displacement of the abomasum. A placebo of the same carrier without bST was administered to control cows in this blinded study. Metabolic and production responses in a short-term follow-up period were measured. Results Blood glucose concentrations in cows 3 to 5 days after surgery were statistically higher for treated cows than for control cows. A higher proportion of treated cows had improved urine ketone test results than did controls. Significant differences in other metabolic values, health, and milk production were not detected. Clinical Implications Treatment of metabolically compromised cows with bST may have some positive effects, but further investigation is needed to confirm therapeutic value. (J Am Vet Med Assoc 1999;214:529–531)