The purpose of this study was to determine whether Freund's complete adjuvant causes adverse effects on the physiology, histology, and activity of rabbits used for polyclonal antibody production. Rabbits in the experimental groups were immunized intradermally and subcutaneously with keyhole limpet hemacyanin with or without Freund's adjuvant. Booster immunizations were administered 28 days after the initial immunizations. No immunizations were administered to rabbits in the control group. Body weight, food consumption, activity, rectal temperature, white blood cell count, corticosterone concentration, and induration around immunization sites were measured. Histologic changes in the lung, kidney, liver, lymph node, and skin were evaluated after euthanasia. There were significant differences in white blood cell count, induration around immunization sites, and lipid droplet deposition in pulmonary microgranulomas in some rabbits that received Freund's adjuvant. These differences did not affect well-being of the rabbits. Freund's complete adjuvant caused no adverse effects on physiologic parameters and activity levels in rabbits; thus, its use in polyclonal antibody production should not be discouraged.