Objective: To determine whether aqueous neem leaf extract (NLE) could induce degeneration of rat oocytes. If yes, whether apoptosis is involved during NLE -induced degeneration of oocytes cultured in vitro. Design: A controlled prospective study. Setting: Laboratory research setting at Department of Reproductive Biomedicine of the Institute. Animal(s): Fifty four sexually immature female rats that were 24-25 days of age. Intervention(s): The immature female rats were injected with 10 IU pregnant mares serum gonadotropin (PMS) for 48 hrs followed by 10 IU of hCG for 16 hrs. After 16 hrs, rats were euthanized; ovulated cumulus oocyte complexes (COCs) were collected from oviduct. Cumulus-enclosed as well as denuded oocytes were used in the present study. Main outcome Measure(s): Rates of shrinkage, membrane leakage, degeneration, assessment of morphological apoptotic changes, bax protein expression and DNA fragmentation. Results: The NLE induced morphological apoptotic changes such as shrinkage, membrane leakage, cytoplasmic fragmentation prior to degeneration of oocytes. The NLE-treated oocytes that had morphological apoptotic features showed overexpression of bax protein, DNA fragmentation as evidenced by TUNEL positive staining and DNA ladder pattern. Conclusion: NLE-induced apoptosis in rat oocytes prior to degeneration in vitro.