The MUTYH gene encodes a DNA glycosylase involved in base excision repair (BER). Biallelic pathogenic MUTYH variants have been associated with colorectal polyposis and cancer. The pathogenicity of a few variants is beyond doubt, including c.536A>G/p.Tyr179Cys and c.1187G>A/p.Gly396Asp (previously c.494A>G/p.Tyr165Cys and c.1145G>A/p.Gly382Asp). However, for a substantial fraction of the detected variants, the clinical significance remains uncertain, compromising molecular diagnostics and thereby genetic counseling. We have established an interactive MUTYH gene sequence variant database (www.lovd.nl/MUTYH) with the aim of collecting and sharing MUTYH genotype and phenotype data worldwide. To support standard variant description, we chose NM_001128425.1 as the reference sequence. The database includes records with variants per individual, linked to available phenotype and geographic origin data as well as records with in vitro functional and in silico test data. As of April 2010, the database contains 1968 published and 423 unpublished submitted entries, and 230 and 61 unique variants, respectively. This open-access repository allows all involved to quickly share all variants encountered and communicate potential consequences, which will be especially useful to classify variants of uncertain significance.