The computerized data base of the Medical Records of the College of Veterinary Medicine at Cornell University was searched from 1976 through 1990, using the diagnostic codes ''muscle atrophy,'' ''diffuse neuromuscular disease,'' ''myopathy,'' ''degeneration spinal nerve root,'' ''degeneration peripheral nerve,'' ''denervation atrophy muscle,'' ''degeneration sciatic nerve,'' and ''emaciation.'' Searching for the diagnoses ''muscle atrophy'' and ''diffuse neuromuscular disease'' revealed seven previously unrecognized equine motor neuron disease (EMND) suspects, beginning with three horses in 1982. The clinical, historic, and pathologic findings in these seven horses were consistent with those of confirmed EMND cases. The failure to find suspect cases prior to 1982 suggests that EMND may be a new disease.