Fingernail deformities secondary to ganglions of the distal interphalangeal joint (mucous cysts). Twenty-six nail deformities secondary to ganglions of the distal interphalangeal joint were retrospectively reviewed to assess the important aspects of their management. The patients' ages ranged from 41 to 79 years. The long and index fingers were most commonly involved. A depression or groove was present in 23 of 26 digits reviewed. Two had gross disruption of the nail. Fifty-eight percent of the cysts had spontaneously drained or had been drained by the patient or a physician preoperatively. Degenerative arthritic changes were seen in 87 percent of those with x-rays or a radiology report available. Most underwent surgical removal of the cyst and debridement of associated osteophytes of the distal interphalangeal joint. The cyst was located above the germinal matrix in all but two digits. Osteophytes were found in all 20 digits in which the joint was explored. No recurrences were seen in those available for postoperative follow-up (22 of 25). Normal nail growth was found in 14 of 22, although follow-up was short in one. All eight postoperative nail deformities were quite mild and of little concern to the patient. There was no correlation between preoperative cyst drainage and aesthetic postoperative nail growth. Nail removal at the time of surgery appeared to be unnecessary unless the nail was grossly disrupted. 