A retrospective survey was performed to assess side effects of alloys used in fixed and removable partial prosthodontics. Nineteen clinicians reported the status of prosthodontic appliances that had up to 31 years of service and the reactions in the corresponding oral mucous membrane. Survey charts of 335 patients, who had a total of 915 fixed and 87 removable prosthodontic units, were received. Almost half of these prostheses were made from base metal alloys, mainly nickel-chromium alloys for the fixed partial dentures, and cobalt-chromium for the removable partial dentures. The rest were classified as gold and palladium-type alloys or as miscellaneous. There were no or only slight deviations from the normal uniform luster of the metal components in all groups. Only four unit were reported to have moderate reactions of severe tarnish and signs of corrosion. The gingiva and oral mucosa adjacent to the restorations were normal but showed slight changes in all groups. Twenty-three of the 335 patients were reported to have moderate reactions, and two patients had severe raactions. The soft tissue reactions were considered to be largely due to factors other than the metal components.