Thirty-eight cases of oral and maxillofacial infections isolated Actinomyces without sulfur granules in the pus or granulation tissue were investigated clinically and bacteriologically in relation to the criteria of actinomycosis and its pathogenesis. These cases were divided into two types from clinical features and course: One was the acute type and the other was the chronic type. The former was clinically similar to the nonspecific acute pyogenic infection, and bacteriologically Streptococci were more predominantly isolated then the latter, together with Actinomyces. The latter clinically resembled actinomycosis and there were less Streptococci. It was thought that in the acute type, Streptococci were preponderant for pathogen, and Actinomyces were part of a mixed infection, while in the chronic type, Actinomyces were preponderant, although no sulfur granules were detected. As process of the infection, the acute type was thought to be in the incipient stage, and the chronic type to be in the later stage These cases were thought to be transitional cases of actinomycosis.
