Objective: Streptococcus pyogenes is the cause of the classical childbed fever and can occur in both sporadic and epidemic form. Once an outbreak is identified on a maternity ward it is not only necessary to place the patients in strict isolation but also identify to the source of the infection. Fast reliable typing methods can aid in infection control. Methods: An outbreak of puerperal fever due to S. pyogenes was analyzed by random amplified polymorphic DNA (RAPD) analysis. Results: Identical fingerprint patterns were found in isolates of 3 patients, the throat and infected finger of the delivering obstetrician, 2 of the physician's family members, and from the cervix of a woman who was examined by the physician 7 months after the outbreak. The outbreak was stopped after antimicrobial treatment of the physician and his family members. Conclusions: RAPD typing appeared to be a fast and reliable tool for epidemiological studies of S. pyogenes and is probably more efficient in strain differentiation than classical M and T serotyping.