The electrodiagnostic differentiation between pronator teres syndrome and entrapment of the median nerve at the ligament of Struthers is generally thought to be aided by the absence of electromyographic (EMG) findings in the pronator teres muscle in pronator syndrome. This report describes a patient with surgically documented pronator teres syndrome who had EMG changes in the m. pronator teres, which was apparently innervated as or after the median nerve passed through. It is concluded that EMG abnormalities in the m. pronator teres should not alone be used to distinguish pronator teres syndrome from entrapment of the median nerve at the ligament of Struthers.