A 59-year-old man admitted for i.m. had a 3-way cannula inserted into the right subclavian vein for 31 days. Autopsy revealed a circular firm thickening of the venous wall. Histology identified it as chondroid and osteoid tissue replacing adventitial connective tissue. Unusual chondroosteoplastic metaplasia not described up to now is discussed as about its causes.