The significance of contact allergy in patients with various oral symptoms was studied. Positive patch-test reactions to mercury compounds were found in 21/91 patients. Of these, 18 had lichenoid lesions in oral mucosa in close contact to amalgam fillings, and three patients with contact allergy had neither amalgam fillings in their teeth nor visible oral lesions. Amalgam replacement was carried out in 15/18 symptomatic patients. The fillings were replaced with gold in three cases, composite resin fillings in six, glass ionomer in three and both gold and composite materials in three cases. In 10 patients there was complete replacement and in five it was restricted to the fillings adjacent to the mucosal lesions. After a mean follow-up period of 3.2 years a complete cure was seen in seven patients, each of whom had had all their fillings changed. A marked improvement occurred in six patients, and there was no change in two.