The Streptococcus milleri group is newly recognized as a cause of pyogenic infection. It is important that microbiologists and physicians become aware of these organisms. The heterogeneous nature of this group of streptococci does mean that laboratories will have to use a combination of antigenic, physiologic, and hemolytic characteristics to identify these pathogenic streptococci. Physicians need to recognize that these microorganisms as a group are able to cause serious infections that may require prolonged treatment and/or surgical drainage of abscesses.