Patients with neurologic signs consistent with previous poliomyelitis have been shown to have electrodiagnostic evidence of widespread denervation, often in clinically normal muscles thought to have been uninvolved by poliomyelitis. Eight percent of patients seen in our postpoliomyelitis clinic had no abnormalities on neurologic examination or with conventional electrodiagnostic studies to corroborate history of poliomyelitis. Seventeen patients were studied, subtle electrodiagnostic evidence of denervation was sought. Measurements of fiber density and analysis of turns and amplitude showed no abnormalities in nine patients. Five patients had borderline elevated fiber density. Analysis of turns and amplitude showed mild neurogenic changes in two patients and borderline changes in three patients. These findings were disparate, with isolated abnormalities in individual muscles. It was concluded that (1) there is a group of patients whose histories of poliomyelitis are uncertain, and (2) the lack of clear evidence for previous denervation after extensive electrodiagnostic testing is a valid means for excluding the diagnosis of postpoliomyelitis syndrome.