The bacterial flora of the vestibule, urethra and vagina of a group of patients with recurrent urethritis, and of control subjects without symptoms, was investigated. Organisms regarded as pathogenic, such as enterobacteria and Streptococcus faecalis, were recovered significantly more frequently from patients than from controls, whereas the reverse was found for non-pathogenic organisms. The bacterial flora was similar in the three areas, suggesting that a specimen taken from one region only would give adequate bacteriological information. The vestibule is suggested as a suitable site. The incidence of vestibular pathogens was higher in postmenopausal patients. Perineal length and vestibular pH were very similar in patient and control groups. There was some evidence that in most subjects the bacterial flora of the areas investigated remains fairly constant over a period of several weeks. Although bacterial species commonly responsible for urinary tract infection may often cause recurrent urethritis, the absence of these pathogens from some patients suggests that the etiology of this condition is not yet fully understood.