A single injection dose-response curve was done in the SJL/J mouse using varying amounts of syngeneic spinal cord homogenate and Mycobacterium tuberculosis H37RA in a Freund's type of adjuvant. Inoculation with as little as 0.025 mg. of cord homogenate induced severe experimental allergic encephalomyelitis in some mice. Possible reasons for the great ease of induction of experimental allergic encephalomyelitis with this single injection regimen in comparison with other single injection schemes are discussed. No single injection dose combination was found that induced severe experimental allergic encephalomyelitis in all of a group of mice. When two injections 1 week apart were given, all mice so injected developed severe experimental allergic encephalomyelitis, all had relapses, and nine of 10 had multiple relapses. The number of relapses and severity of residual neurologic deficits were much greater in the two-injection group than in the single injection group.