A total of 375 anaerobic and microaerophilic coryneform rods, isolated from the pilosebaceous ducts of 26 healthy persons (71 strains) and from comedones (93 strains), pustules (107 strains), and the unaffected skin (104 strains) of 36 acne patients were classified according to the species key in Bergey's manual, the biotyping scheme of Pulverer and ko, the serotyping schedule of Höffer et al., and the phage typing schedule of Jong et al. The statistical evaluation demonstrated certain differences in the frequencies of the Propionibacterium species and types between the different groups tested. Thus, the species P. granulosum was isolated only from acne patients (50.0% of patients examined) and was found more frequently in comedones and pustules than in unaffected follicles in acne patients. The majority of P. granulosum strains belonged to serotype II (95). Biotype A propionibacteria were more frequently found in strains from healthy controls (52.1% of strains) than in strains from healthy controls (52.1% of strains) than in strains from comedones (17.2%), pustules (27.1%) and unaffected skin (38.5%) of the acne patients. The results of phage-typing showed that the P. acnes lysotype I was more frequent in acne patients (total: 73.2% of strains), especially in the inflamed pustules (88.5%), than in healthy controls (55.1%).