Multiple sequence alignment among 12 complete SARS coronavirus (SARS-CoV) sequences reveals that the major parts of 29708 b of the genomes have 99.82% identical bases. Forty two nucleotide mismatches were found in addition to the five and six gaps in two genomes. Among them, 28 mismatches result in changes of amino acid in the encoded proteins. Analysis of the changes implies possible effect on the Spike and Membrane protein of the virus, while most of the other changes seem not very significant to alter the structure and function of the proteins. These results have been released on the anti-sars web site maintained by the Centre of Bioinformatics, Peking University (antisars.cbi.pku.edu.cn) and may be of help for further experimental study.