A 42-year-old man presented with painful toenails which were overcurved transversely and onycholytic. Examination revealed that all toenails, the thumbs and index fingers were similarly affected. In addition, he had a small area of leukokeratosis in the mouth, epidermal cysts of the scrotal skin and a small area of hyperkeratosis on the ulnar borders of his hands. His characteristic nail changes began in the great toenails at the age of 20 years. After renal transplantation at age 39, the other nails changed and he developed the features described above. His sister has overcurvature of the fifth toenails. A diagnosis of pachyonychia congenita tarda was made. His case is compared with 14 other reported cases of this rare syndrome.