Mutations in the SMAD4 gene have been found in patients with Juvenile Polyposis Syndrome (JPS), patients with combined Juvenile Polyposis/ Hereditary Hemorrhagic Telangiectasia (JP/HHT) or patients with HHT, but without reported symptoms of juvenile polyposis. We have developed a publicly available, searchable SMAD4 database to aid in genotype/phenotype correlations, using the Human Genome Variation Society recommendations for mutation nomenclature and database content. The purpose of this database is to serve as a repository for all known SMAD4 mutations, variants of uncertain signi fi cance, or polymorphisms including sequence based changes and large deletion/ duplications that have been linked to JPS, JP/HHT, or HHT as well as any clinical information or signi fi cant literature related to the disorder. Each database entry lists the SMAD4 mutation’s location, mutation type, pathogenicity classi fi cation, disease-speci fi c phenotype, literature references, and comments (which may include clinical features, complex genotypes, and links to additional literature references). The majority of the SMAD4 database entries consist of missense sequence changes and small deletions with 67 JPS mutations, 23 JP/HHT mutations, and one HHT-causing mutation. Novel SMAD4 variants and updated phenotypic information for any existing database entry can be submitted electronically on the database website (www.arup.utah.edu/database/SMAD4/SMAD4_welcome.php). In conclusion, with links to detailed clinical descriptions and all published references, this database hopes to serve as a valuable reference for the clinical management of patients with JPS, JP/HHT and HHT.