Abstract: The anticoccidial efficacy of natural herb extracts was evaluated in suckling calves with bovine coccidial infection (Eimeria sp., including E.bovis and E. zuernii). The herb extracts were orally administered to 5 calves (treatment group) for 7 weeks and the clinical signs, oocyst excretion and blood parameters, which reflect hepatic and renal functions, as well as nutritional condition and body weight gain of the treatment group were compared with those of untreated 5 calves (control group). During the experimental period, all the 5 calves in the control group had bloody diarrhea accompanied with remarkable oocyst excretion. None of the 5 calves in the treatment group had bloody diarrhea. No significant differences were observed in the blood parameter results between the 2 groups. The results of this study indicate that the daily administration of herb extracts to calves from the suckling to weaning period is effective in preventing bovine coccidial infection.