1. Although CoV-HKU1 was not identified in any of the studied animals, a coronavirus closely related to SARS-CoV (bat-SARS-CoV) was identified in 23 (19%) of 118 wild Chinese horseshoe bats by reverse transcriptase polymerase chain reaction (RT-PCR). 2. Complete genome sequencing and phylogenetic analysis showed that bat-SARS-CoV formed a distinct cluster with SARS-CoV as group 2b coronaviruses, distantly related to known group 2 coronaviruses. 3. Most differences between the bat-SARS-CoV and SARS-CoV genomes were observed in the spike gene. The presence of a29-bp insertion in ORF 8 of bat-SARS-CoV genome, not in most human SARS-CoV genomes, suggests that it has a common ancestor with civet SARS-CoV. 4. Antibody against recombinant bat-SARS-CoV nucleocapsid protein was detected in 84% of Chinese horseshoe bats using an enzyme immunoassay.Neutralising antibody to human SARS-CoV was also detected in those with lower viral loads.5. This study also revealed a previously unknown diversity of coronaviruses in bats, which are important natural reservoir for coronaviruses including SARS-CoV-like viruses.