A new autosomal recessive mutation, characterized by an early defect in righting reflex and stiffened gait, progression to severe spasticity, tremor and rigidity, and death before weaning, appeared spontaneously on the C57BL/6 background. It was shown to be an allele of the mutant spasticspa, and shall be known asspaAlb. Mutant levels of [3H] strychnine binding are less than 10% of control levels in the brainstem and spinal cord. Autoradiographic examination of the distribution of [3H]strychnine binding sites in the mutant confirm a greatly reduced level of binding compared to control in all areas of the spinal cord, brainstem, and midbrain.