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Multiple exposures to the herbicide atrazine (ATRZ) were shown to suppress the LH surge in both cycling female rats and those ovariectomized (OVX) and primed with estradiol (E-2). A single ATRZ administration was found to induce a prompt and marked increase in progesterone (P-4). As exogenous P-4 is known to have a differential effect on the LH surge depending on its temporal relationship with the surge, it was hypothesized that a single treatment in an OVX, E-2-primed rat would augment the surge, whereas several exposures would cause a decrease. Following four daily treatments with 100 mg/kg, LH surge was suppressed. In contrast, a single ATRZ exposure elevated the surge. Two treatments were without effect. The single administration caused a large increase in P-4 at 30 and 60 min that was likely attributable to adrenal secretion. Four exposures also elevated P-4 after the final treatment, although the duration of the increase was shortened. A single treatment with 0, 10, 30, and 100 mg/kg ATRZ showed similar elevations at the highest concentration in P-4, the LH peak, and area under the curve (AUC), whereas four exposures reduced the AUC. An increase at 1 h in the expression of Kiss1 in the anteroventral periventricular nucleus suggests that this regional kisspeptin neuronal population has a role in the ATRZ augmentation of the surge. These data support the hypothesis that ATRZ-induced changes in adrenal P-4 can either augment or attenuate the surge depending on the temporal proximity of exposure to the rise in LH.