In the light and electron microscopical study reported here, we documented the structure of the nucleus, nucleolus and nuclear channel system (NCS) in the uterine glandular epithelium in both fertile and infertile women during the early luteal phase. Nuclear volume was found to be larger in the infertile group at day 5 after the luteinizing hormone surge (LH+5) compared to day-matched fertile subjects. A two-way analysis of variance performed on nucleolar volume data from fertile and infertile women biopsied on days LH+5, +5, and +6 revealed a significant effect of condition but no effect of day or interaction. Nucleolar volume decreased from day LH+2 to day LH+6 in the fertile group, the sharpest decrease occurring between day LH+3 and day LH+4. The largest mean volume of the NCS was found at day LH+5 in the fertile group and day LH+6 in the infertile group. The results suggest a delay in the development of this organelle in the infertile women. The present study has documented alterations in the nuclei of uterine glandular cells from infertile patients. In these infertile women, there is also a delayed elaboration of the secretory apparatus and this delay correlates well with the delayed/reduced expression of a luteal-specific glyco-protein.