Familial acromegaly is a very rare inherited disorder, characterized by the clustering within a single family of several related cases with somatotroph adenomas and acromegaly. The causes of these dominantly inherited pituitary tumours remain unknown. Although these families have a clinical presentation distinct from that of multiple endocrine neoplasia type 1 (MEN-1), the question of this syndrome as being linked to the MEN-1 locus has remained open. Our aim was to study a three-generation family with cases of acromegaly in a mother and her son, to explore better the clinical presentation of the disease, its pattern of inheritance and to test the hypothesis of a genetic linkage to the MEN-1 locus using closely linked polymorphic genetic markers. The refined analysis of 15 unaffected relatives revealed miscellaneous non-specific endocrine dysfunctions and the presence of multiple lipomata, as noted previously in some cases. Moreover, the notion of acromegalo-gigantism in the maternal grandmother and an incomplete penetrance appeared even more typical, suggesting that familial acromegaly is a specific clinical entity. Finally, under the hypotheses assumed for segregation analysis, no clinical, biological or genetic evidence of linkage to the MEN-1 locus could be retained in this family. However, these conclusions were limited because of incomplete penetrance and uncertain definition of the carrier status. Therefore, we conclude that further identification of the genetic predisposition to familial acromegaly might be obtained from the combined molecular genetic analysis of several families presenting with the same clinical features.