MEN1 is the causative gene for multiple endocrine neoplasia type 1 (MEN1), a hereditary syndrome characterized by hyperplastic and neoplastic disorder of endocrine organs such as parathyroid, anterior pituitary and gastroenteropancreatic endocrine tissues. More than 300 germline mutations have already been reported in patients with MEN1. We here report a novel deletional mutation identified in a Japanese woman with apparently sporadic recurrent hyperparathyroidism. Genetic testing revealed a heterozygous deletion involving 14 bp in exon 6 (starting at amino acid codon 293) of MEN1, which results in early termination of the protein. This deletional mutation has not previously been described elsewhere.