The final stages of follicular and oocyte maturation, ovulation, and fertilization take place during a narrow window of time, typically less than 24 h in rodents. These events, which are a prelude to normal embryonic development, can potentially be targeted by environmental contaminants or pharmaceuticals in a variety of ways, resulting in infertile reproductive cycles or developmental disorders in offspring. This chapter synthesizes experimental evidence, where available, for specific compounds targeting preovulatory follicles, the ovulatory process, or oocytes. We also point out biologically plausible sites and modes of potential toxicant-induced insult based upon studies with experimental chemicals. We hope this approach will stimulate further research focused on how acute toxicant exposure during brief but critical periods of oocyte development might derail these essential processes and place the female at risk for reproductive failure.