Germline mutations of the MEN 1 gene are responsible for multiple endocrine neoplasia type 1 (MEN 1), a dominantly inherited cancer syndrome characterized by tumors of the parathyroids, gastro-intestinal endocrine tissue, anterior pituitary and other endocrine tissues. We report on a 55-yr old woman, presenting with active acromegaly (due to GH-secreting microadenoma), associated to bilateral adrenal adenomatosis and Hürthle-cell thyroid neoplasia. No evidence of hyperparathyroidism or gastrin-secreting tumor was found. Peripheral blood genomic DNA was extracted, amplified by PCR, purified and analyzed by direct sequencing. The analysis revealed a heterozygous mutation in exon 4 of the MEN 1 gene: a G to A missense mutation at codon 229 (CGC-->CAC), which changes arginine to histidine. This mutation causes loss of the Hhal restriction site and can thus be employed for a rapid familiar screening. This case represents a newly recognized germline mutation of the MEN 1 gene.