The aims of this study were [1] to test the feasibility of autologous heterotopic transplantation of large ovarian tissue samples (approximately 2 cm in diameter and 2 or 3 mm thick) without vascular anastomosis and [2] to compare follicle count and microvessel density in fresh and grafted 2-mm vs. 3-mm tissue samples in an animal model. After transplantation, we observed regular menstrual cycles and ovulation proved by high E(2) levels and intermittent P peaks in all Suffolk sheep, and histologic examination revealed no statistically significant differences in the number of primordial follicles and microvessel density between samples 2 mm and 3 mm in diameter.