The single nucleotide polymorphisms (SNPs) in conserved protein regions have been thought to be strong candidates that alter protein functions. Thus, we have developed SNP@Domain, a web resource, to identify SNPs within human protein domains. We annotated SNPs from dbSNP with protein structure-based as well as sequence-based domains: (i) structure-based using SCOP and (ii) sequence-based using Pfam to avoid conflicts from two domain assignment methodologies. Users can investigate SNPs within protein domains with 2D and 3D maps. We expect this visual annotation of SNPs within protein domains will help scientists select and interpret SNPs associated with diseases. A web interface for the SNP@Domain is freely available at http://snpnavigator.net/ and from http://bioportal.net/.This project was supported by the Korean Ministry of Science and Technology (MOST) under grant number M10508040002-05N0804-00210 and M10407010001-05N0701-00100. Y.B.C. is supported by Biogreen21 program (20050401-034-791-006-03-00 and 20050301-034-481-006-02-00). Funding to pay the Open Access publication charges for this article was provided by M10407010001-05N0701-00100 grant of MOST