Résumé : By electron microscopy, the intracellular structure previously observed on H. influenzae spheroplasts by phase contrast and acridine stain, is confirmed. The spheroplasts correspond to reversible L forms. Very few elements reverse to bacillary form. The observation of a large number of bacteria is possible with acridine stain and the detection of reversible elements also. In these conditions acridine stain completes electron microscopy. The importance of Hemophilus spheroplasts in chronic bronchitis should be determined.