Suggested biological test methodology and reported side effects of alternative dental alloys, i.e. those with less than 75 per cent noble metal content, are reviewed. The recommended biological assessments aim to evaluate systemic toxicity, local irritation, carcinogenicity and allergic responses. The most likely side effect following the use of alternative alloys in dental prosthetics is an allergic reaction. The frequency of this side effect is not known but it is considered to be low.