SummaryUniformly successful production of rabbit rhinovirus antisera depended on production of immunogens with virus concentrations of at least 107 pfu/ml. Response in pairs of rabbits immunized with the same antigen appeared to be remarkably uniform, and maximum antibody titers were attained at 38 to 45 days after beginning a relatively simple immunization schedule (1 im + 4 iv injections). Anticellular antibody levels were usually low in comparison to rhinovirus antibody titers and such antibody could be removed easily by adsorption with suspensions of whole HeLa cells without reducing the level of antiviral antibody.The authors express their appreciation to Prudence Moeller Olsen, Marie Morasch, and Byron Doneen for valuable technical assistance.