Using Streptococcus sinensis 16S rRNA-specific and groEL gene-specific primers, a 128-bp fragment of the 16S rRNA gene and a 433-bp fragment of the groEL gene were amplified from bacterial DNA recovered from 22 of 100 saliva samples from healthy volunteers. There was no nucleotide difference between the 88-bp 16S rRNA gene fragments from the 22 saliva samples and that of S. sinensis strain HKU4(T), but there were zero to eight nucleotide differences between the 311-bpgroEL gene fragments from the 22 samples and that of S. sinensis strain HKU4(T). The oral cavity is the natural reservoir of S. sinensis.