The condition of experimental allergic encephalomyelitis (EAE) induction was investigated in several mice strains. SJL and C3H/He strains were found to be susceptible. A single immunization with mouse spinal cord, complete Freund's adjuvant (CFA) and pertussis vaccine produced clinical signs of EAE in SJL and C3H/He strains after 11 to 18 days. Isogenic spinal cord produced EAE in C3H/He strain. A single immunization with myelin basic protein from bovine spinal cord in CFA and pertussis vaccine produced EAE in SJL strain. EAE susceptibility of SJL strain correlated with the amount of mycobacteria used for sensitization. It was necessary to give pertussis vaccine intravenously in all cases.