We investigated the pattern of reactivity of calretinin and CD34 in normal and pathological endometria.Various endometrial tissues were submitted for calretinin and CD34 immunostaining.Calretinin reactivity was limited to the endometrial stromal cells (ESC) of the superficial zone of the functionalis layer (FL) in the proliferative phase, and was extensive in all stages of the secretory phase. The ESC of the post-menopausal, ectopic, hyperplastic or neoplastic endometria showed negative or focal weak reactivity for calretinin. In dysfunctional uterine bleeding (DUB) with a normal or an abnormal histopathological appearance on routine stain, there were varying degrees of focal to extensive decreases in calretinin reactivity. The foci of negative calretinin reactivity in the FL displayed varying reactivity for CD34 and appeared to be continuous with the basalis layer (BL). Endometrial polyps were often reactive for CD34, but not reactive for calretinin.Immunostaining for calretinin and CD34 is helpful in the diagnosis of endometrial polyp and hyperplasia. In DUB, with or without abnormal histopathological findings, there were alterations of the zonal pattern of calretinin reactivity in the FL. This alteration appears to be an expansion of the stroma of the BL into the FL, resulting in a 'disordered endometrial stroma'.