To study the efficacy monoclonal antibody(MAb) against bovine rotavirus(BCV) in treatment of calf diarrhea, the MAb was fed to 166 calves with diarrhea from Chung-buk area. The results were summarized as follows. 1. Among the 1,049 calves investigated, 166(16%) calves were infected with BCV. 2. The monthly rate of BCV infection were higher in October to December compared with other months of the year. 3. Among the 166 calves with diarrhea, 137(83%) calves were recovered. 4. Young calves within 7-day-old were more effective in treatment than other ages and the rate of treatment was 86% 5. Most effective period for treatment of rotavirus was at the first stage of infection.