We present the clinical criteria for diagnosing bacterial vaginosis (BV). Variablility of adhesion of Gardnerella vaginalis, Lactobacillus, Candida albicans to vaginal epithelial cells is discussed. We describe and compare images of clue cells in: direct vaginal smears in contrast phase microscopy, direct smears stained with methylen blue and traditional smears stained with hematoxylin-eosin (H-E). The value of combined colposcopic-cytological examination in differential diagnosis of BV and vaginitis is emphasized.