During a period of 25 years, 500 dorsal ganglions of the wrist were treated surgically. Three hundred and forty-six were followed for a minimum of 9 months; there were three recurrences. Dissection of the cysts under magnification of six to 25 times and serial microscopic studies showed evidence of a one way, valvelike system between the scapholunate joint and the ganglion. Stress, as a cause of ganglions, is suggested. Operative treatment involved excising all attachments to the scapholunate ligament.