During a 5-year period, 33 patients with pain in the palmar aspect of the wrist and forearm with and without features of carpal tunnel syndrome were diagnosed as having restrictive thumb-index flexor tenosynovitis. The pathognomonic sign in this condition was the simultaneous flexion of the index finger with active flexion of the thumb across the palm. Treatment included either steroid injection into the tendon sheath of the flexor pollicis longus or surgical exploration of the palmar aspect of the distal forearm and wrist region. Twenty-six wrists in 24 patients were surgically explored, and all had hypertrophic tenosynovium between the flexor pollicis longus and index profundus tendons. More than half of the explored wrists had a tendinous connection between the flexor pollicis longus and the flexor profundus of the index digit. Of 17 wrists with follow-up of more than 6 months, 13 were improved by surgical management. Steroid injection did not have a long-term effect.