The G(M2) gangliosidoses are a group of recessive disorders characterized by accumulation of G(M2) ganglioside In neuronal cells. The genes responsible for these disorders are HEXA (Tay-Sachs disease and variants), HEXB (Sandhoff disease and variants), and GM2A (AB variant of G(M2) gangliosidosis). We report the establishment of three relational locus-specific databases recording allelic variation at the HEXA, HEXB, and GM2A genes and accessed at the G(M2) gangliosidoses home page (http://data.mch.mcgill.ca/gm2-gangliosidoses). Submission forms are available for the addition of-new mutations to the databases. The databases are available online for users to search and retrieve information about specific alleles by a number of fields describing mutations, phenotypes, or author(s).