Cervical and cortical somatosensory evoked potentials were measured in 80 patients with suspected or established multiple sclerosis (MS). The cervical response was a more sensitive diagnostic indicator than the cortical response, and was abnormal in 86.7 percent of patients with definite MS and in 40.9 percent of MS suspects. The complementary value of measuring both responses was greatest (89.3 percent) in early probable or latent MS. Comparing the responses obtained from stimulation of the left and right extremities increased the overall diagnostic yield by 25 percent. Abnormal responses were frequently obtained from clinically normal limbs.