Introduction: The effects of different doses of oestrogen on the endometrium of women with premature ovarian failure have been examined in this study. Materials and Methods: Four groups of women of reproductive age were studied; 1 normal fertile controls 2. patients given a standard, variable hormone replacement therapy (HRT) 3. a group given a fixed daily dose of 1 mg of oestrogen and 4. a group given a fixed daily dose of 4 mg of oestrogen. Endrometrial diposises were taken at a bout 5-6 days after ovulation and tissue was prepared for light and electron microscopy. Morphometry was used to evaluate quantitatively various features of endometrial luminal epithelial cells. The volume fraction (Vv) of nucleus to cell in the standard group was significantly larger than the 4 mg group. Results: The Vv of euchromatin to nucleus was larger in the controls and 4 mg group than the 1 mg subjects. The Vv of mitochondria to cell was largest in the control group. The ratio of desmosomes to surface membrane was increased (P<0.05) in the 1 mg subjects. Conclusion: These results suggest that, while standard HRT is generally a good mimic of controls, the 1 mg fixed dose delayed some membrane features and the fixed 4 mg group showed advancement in some organelle growth.