In the first part of this thesis, we utilize the mouse model to evaluate the environmental chemical Butyl Benzyl Phthalate. Due to lack of research on female exposure to BBP, this thesis focuses on quantifying the effects of gestational exposure on the female mammary gland Here male and female parental mice were exposed before mating and through pregnancy and lactation to one of three doses of BBP or the control via oral ingestion. After weaning, offspring were sacrificed at puberty or early adulthood and evaluated for altered mammary gland morphology or hormonal receptor expression. Results indicate a persistent statistically significant increase in weight among the highest BBP dose group. Additionally, the high-dose adult treatment group demonstrated a statistically significant decrease in terminal ends. Finally, the mid-dose adult group demonstrated significantly higher expression of the progesterone receptor compared to the low and high-dose BBP groups. There were no significant findings in pubertal female outcomes. In the second part of this thesis, we evaluate the existing OECD Extended One-Generation Reproductive Toxicity Guidelines (TG 443). First by summarizing the endpoints and outcomes evaluated in studies that implement these guidelines, and additionally discussing the current OECD recommendations for mammary gland evaluation. We conclude with outlining the remaining questions to be evaluated and further research necessary to establish that the mammary gland should be added to TG 443.