Severe acute respiratory syndrome (SARS) caused by SARS-associated coronavirus (SARS-CoV) is a fatal disease. Prevention of future outbreaks is essential and requires understanding pathogenesis and evolution of the virus. We have isolated a SARS-CoV in China and analyzed 47 SARS-CoV genomes with the aims to reveal the evolution trends of the virus and provide insights into understanding pathogenesis and SARS epidemic. Specimen from a SARS patient was inoculated into cell culture. The presence of SARS-CoV was determined by RT-PCR and confirmed by electron microscopy. Virus was isolated followed by the determination of its genome sequences, which were then analyzed by comparing with other 46 SARS-CoV genomes. Genetic mutations with potential implications to pathogenesis and the epidemic were characterized. This viral genome consists of 29,728 nucleotides with overall organization in agreement with that of published isolates. A total of 348 positions were mutated on 47 viral genomes. Among them 22 had mutations in more than three genomes. Hot spots of nucleotide variations and unique trends of mutations were identified on the viral genomes. Mutation rates were different from gene to gene and were correlated well with periodical or geographic characteristics of the epidemic.