The therapeutic effects and immune responses with Oidenlandiae Herba administration(17.5%, 1g/30 kg, everyday, PO) were investigated in calves(1 to 3 months old) with diarrhea from 159 Korean native calves(76 heads from A farm and 83 heads from B farm) in Jeju. The causes of 47 calves with diarrhea were coronavirus(1 head) and rotavirus(1 head), coccidium(5 heads) and bacteria(40 herds). PCV values were significantly increased 2 weeks after administration of Oldenlandiae Herba in A form, compared by those of pre-treatment(p<0.05). However RBC, TP, WBC, fibrinogen levels were not significantly changed. The significant difference were not detected in changes of AST, BUN and creatinine. The CD14+ distribution rate were increased in 1 week after administration of Oldenlandiae Herba, compared by that of pre-treatment(p<0.05), however, certain tendencies of changes were not observed in distribution rates of CD4+ CD8+ and CD19+, respectively. The rate of death was 20.1%(36/179 calves) in 2004, however, it was decreased to 12.6%(20/159 calves) by Oldenlandiae Herba administration at 2 farms from Jeju in 2005. In conclusion, the administration of Oldenlandiae Herba was effective for treatment of calves with diarrhea.