In this study structural alterations were tested on anovulatory infertile women who had undergone treatment of HMG + HCG to induce ovulation and subsequently to achieve pregnancy. For this purpose, a single premenstrual endometrial fundal biopsy was performed and evaluated using light and electron microscopy. The aim of the study was to evaluate the biopsies with respect to 'in-phase' or 'out-of-phase' at light microscopic level, in which a series of strict criteria were chosen, and then to detect the additional structural abnormalities at electron microscopic level, if present. Only one of the women in our study who had an in-phase endometrium became pregnant after proper treatment protocol individually adjusted and consequently terminated by an early abortion. Histologic features of the biopsies revealed that about half were normal while the rest had various types of structural abnormalities in the transformation of the secretory endometrium detected by light and/or electron microscopy. At the electron microscopic level, multiple alterations were seen in cellular and intercellular components even in those diagnosed as normal by light microscopy. As a result of the above data it was concluded that the cause of inconceivability might arise from some fine structural alterations which may affect the endometrial receptivity of an implanting embryo.