The objective of this thesis is to characterize the effects of waterborne progesterone exposure on zebrafish (Danio rerio) reproduction. Short-term spawning bioassays showed a reduction in spawning after exposure to waterborne progesterone for 3, 7 and 14 days. While the whole organism level response of egg production showed a consistent response, other endpoints did not. Changes in ovarian testosterone and 17β-estradiol (E2) were not explained by changes in the ovarian expression of selected enzymes responsible for the production of hormones such as hydroxysteroid 17-ß dehydrogenase-3 (17βHSD-3) or aromatase. Likewise, the reduction in spawning success was not associated with alterations in ovarian expression of select genes involved in oocyte growth, maturation and ovulation. While findings related to gene and hormone effects remain inconclusive, the results of this thesis provided support for the use of spawning success as a whole organism endpoint to study the effects of EDCs on reproduction.