The genetic abnormality of multiple endocrine neoplasia type 2A (MEN 2A) has recently been elucidated. Over 95% of families with MEN 2A have an identifiable mutation of the RET proto-oncogene on chromosome 10. This report describes a black South African woman with MEN 2A in whom a mutation of the RET proto-oncogene was identified. Current genetic knowledge and recent changes in clinical practice are presented, with specific reference to the other family members found to be carrying the mutant RET gene.