Strains of streptococci were isolated from the mouths of children attending the United Dental Hospital, Sydney, Australia. These strains were analysed biochemically using the Rapid ID32 Strep microsystem, were subjected to DNA-DNA hybridization with other members of the oral streptococci and had their 165 rRNA analysed. On the basis of DNA-DNA hybridization, their nearest relative was Streptococcus parasanguinis, whereas, on the basis of 16S rRNA analysis, it was Streptococcus infantis. The name Streptococcus australis sp. nov. is proposed for the new species. The type strain is AI-1T (= ATCC 700641T = NCTC 13166T).