Sixty-five patients with premature rupture of the membranes were studied. Vaginal smears were evaluated with regard to their general aspect, the staining of cellular elements, and the presence of flora, leukocytes, red cells and squames. In two-thirds of the patients special features were observed: dispersal of clumps, weakly staining nuclei and cytoplasm, and a reduction of or the disappearance of the flora. In one-third of the cases, vaginal smears had a normal pregnancy aspect. The cytologic aspects described may be of help in diagnosing certain cases of premature rupture of the membranes.