Objective: To evaluate the impact of the number of retrieved oocytes on pregnancy outcome. Materials and Methods: We retrospectively examined the cycles of 2491 women undergoing in vitro fertilization therapy at Taipei Medical University (Taipei, Taiwan) from August 1995 to March 2009. We divided them into three groups based on their response rate (where H = high, M = middle, and L = low). We conducted this study to evaluate and compare pregnancy outcome in these three groups. Results: The total number of retrieved oocytes had a significantly positive correlation with peak E2 levels, and the number of fertilized oocytes, good quality embryos, and available frozen embryos. The number of retrieved oocytes had a positive correlation with pregnancy rates and a negative correlation with fertilization rates. The implantation and abortion rates among the three groups were essentially the same. Compared to the middle and higher responders, the pregnancy rates for lower responders were significantly lower. The pregnancy rates for middle responders and higher responders were not significantly different. Conclusion: The benefits of more retrieved oocytes between the lower and the middle responders were obvious. However, the benefits and risks for retrieving more oocytes for the middle and the higher responders remained controversial.