Antigen stimulated lymphocyte cell culture transfer factor, purified by gel filtration and lymphocyte lysate transfer factor, purified by dialysis, was used in efforts to transfer immunity to rabies virus adoptively in various laboratory and wildlife animals. Transfer factor activity was measured by observing the mortality ratio of treated and untreated animals challenged with CVS-27 rabies virus, by the lymphocyte proliferation assay and by the indirect leucocyte migration inhibition assay;Efficacy studies based on mortality data were inconclusive. Transfer factor may have been responsible for the resistance observed in some experiments. Resistance appeared to be inhibited in two trials performed in mice. Both specific and nonspecific enhancement of lymphocyte activity was observed after in vivo administration of TF. No in vitro lymphocyte stimulation was observed.