Objective: Over the last decade there has been an increasing number of patients aged 80 years and over undergoing heart valve replacement. However, literature on the outcome of mitral valve replacement (MVR) in this age group is still limited. Methods: We conducted the present study by analysing data extracted from the UK Heart Valve Registry. From January 1986 to December 1994, 86 patients underwent isolated MVR and 10 underwent combined MVR with aortic valve replacement (AVR) and were reported to the Registry. Results: The 30 day mortality was 10.4% (9/86) in the MVR group and 10% (1/10) in the MVR and AVR group. The actuarial survival was 79.8, 64.1 and 40.7% at 1, 3 and 5 years, respectively, in the MVR group. Of the 10 early (30 day) deaths, 8 were due to cardiac reasons and 19 of the 28 late deaths were due to non-cardiac reasons. A total of 55 (57.2%) patients received a bioprosthetic valve implant and 41 (42.8%) patients received a mechanical valve implant. There was no difference in survival between the two groups. Conclusions: The above results suggest that MVR in octogenarians produces a satisfactory early postoperative outcome and moderate medium-term benefit. There is no difference in survival between patients receiving bioprosthetic and patients receiving mechanical valve implants. © 1997 Elsevier Science B.V.