In about 5% of 3355 patients the microscopic examination of the vaginal discharge in normal saline showed a characteristic fast moving rod. More than 80% of these patients complained of a discharge with a foul smell during the menstrual period. Bactriology showed an anaerob gram negative rod which was difficult to grow and is as yet unclassified. Following treatment with one gram of Mimorazol every 12 hours for 3 doses, 71,5% of the patients were cured and showed a normal vaginal flora without further treatment. In around 24,13% of the patients the gram negative rod disappeared but a persistent mixed flora required further treatment. In 4.3% of the patients a recurrence occurred. An attempt was made to prevent recurrent infection prior to the follow-up examination by prohibition of sexual intercourse with an untreated partner, bathing in public swimming pools, and the use of sponges or wash cloths. In the course of the investigation the suspicion of contamination from the water of public pools became apparent. The diagnosis, treatment and transmission and the pathogenecity of the fast moving negative rod is discussed.