In 1978 five cases of so-called hypersensitivity reactions to Scutan and two to Impregum were reported (Dahl, 1978). The aim of the present study was to assess whether hypersensitivity or cell-mediated immune reactions were associated with the adverse clinical reactions in these patients or in others who had experienced the same reactions. Epicutaneous patch testing and lymphocyte transformation tests were carried out in a total of 13 individuals. The findings were difficult to interpret, because there was no consistent association between skin reactions and cell-mediated immune responses in subjects with suspected allergies. Other possible reasons for the reactions originally recorded were therefore discussed. It was concluded that adverse reactions associated with immune-mediated, delayed type hypersensitivity reactions may be elicited by prosthodontic materials, but other pathogenic mechanisms and aetiological factors responsible for the reactions observed should also be considered.