The effect of levamisole in calves experimentally infected with bovine viral diarrhea virus was evaluated in a double-blind study. The infection was mild and there was no difference in severity of infection or speed of recovery between levamisole-treated and 0.9% NaCl solution-treated (control) calves. Also, the serum antibody titers and viral recovery data of these calves were comparable. The white blood cell counts were consistently higher in the treated group than in the control group, with the difference peaking on postinoculation day 15. The detection of marked lymphopenia in control calves but not in levamisole-treated calves indicated a potential use of levamisole in bovine viral diarrhea.