79 patients (101 hands) who required treatment of idiopathic carpal tunnel syndrome were randomized to receive either endoscopic (ECTR) or palmar incision open carpal tunnel release (OCTR) to determine the effects of Okutsu-method ECTR on postoperative outcome. The results indicated that early improvements in muscle strength were achieved with the ECTR procedure, but with an elevated risk of exacerbation of subjective symptoms and nerve latency as a result of transient nerve dysfunction. The study demonstrated that caution must be exercised when using ECTR in patients who have been identified preoperatively as electrophysiologically compromised.