Multiple endocrine neoplasia type 1 (MEN 1) is a familial cancer syndrome characterized by parathyroid hyperplasia, pituitary adenomas, and neuroendocrine tumors of the pancreas and duodenum. In 1997, the MEN1 tumor suppressor gene was identified, and numerous germline mutations have been reported to be distributed throughout the gene. We used single strand conformational variant (SSCV) analysis to search for germline mutations in the members of 33 kindreds with a confirmed diagnosis of MEN 1. SSCV analysis revealed 25 conformational variants representing germline mutations that are predicted to result in loss of normal menin function. Twenty different disease-associated mutations were identified: five resulting in potential abnormal RNA splicing, two missense mutations, seven nonsense mutations, and six frameshift mutations. The aberrant splice products were identified and confirmed by RT-PCR and direct sequence analysis for two of the five splice mutations. Sixteen of the 20 (80%) mutations identified have not been previously reported. Mutations were not identified in eight kindreds with signs and symptoms consistent with MEN 1. The SSCV analysis revealed mutations in 76% (25 of 33) of the kindreds investigated, thus showing SSCV analysis to be a reliable mutation detection strategy. One-fifth of the mutations identified in this study involve intron sequences, therefore, highlighting the importance of including intron sequences in the search for germline mutations in the MEN1 gene. The need to investigate the entire gene when characterizing new MEN 1 families presents challenges in the translation of genetic studies to efficient clinical diagnostic tests.