Familial acromegaly is an exceptional clinical entity when not associated with features of multiple endocrine neoplasia type 1 (MEN1). We report here 3 pedigrees in each of which 2 patients have been shown to develop acromegaly. In 4 patients, clinical follow-up, and biological screening allowed to confidently exclude MEN1. Absence of mutation in the MEN1 gene after direct DNA analysis in 2 pedigrees reinforces the conviction that the families do not have MEN1. In families 1 and 2, diagnosis was made at a very early age and voluminous adenomas with suprasellar expansion were already present at the time of diagnosis. We review the 20 previous reports of familial acromegaly, some of them questionable. Our 3 families, combined with some other published pedigrees, allow the delineation of a familial form of acromegaly, distinct from MEN1. Dominant inheritance with reduced, age-dependant penetrance is the most parsimonious model to explain the recurrences. Gs protein pathway could be the site of action of the gene responsible of familial acromegaly, but no data have been published to sustain or reject this hypothesis.