Atrazine and chlorpyrifos are a commonly used herbicide and pesticide, respectively. Mammalian studies have found similar effects from these chemicals including reduced birth weight of offspring and reduced numbers of viable offspring. Additionally, invertebrate and fish studies have found synergistic toxicological effects. It was hypothesized that these chemicals would not individually have statistically significant effects but the combined group would experience effects on birth weight of pups and number of pups born as a result of synergistic effects. This study examined the effect of these two chemicals in Sprague Dawley rats at levels of 25mg/kg of body weight for atrazine and 5mg/kg for chlorpyrifos. Four groups were established: a control receiving corn oil, a group receiving only atrazine, a group receiving chlorpyrifos, and a group receiving both chemicals. Subjects were exposed for three weeks prior to impregnation and throughout term. No statistically significant differences were found among any of the groups in number of offspring per litter or average weight of pups. Future studies could increase the concentrations of these chemicals to examine effects at higher dosages; however, higher doses lose relevance to possible environmental exposure.