The decline in frog populations is a well-recognized worldwide phenomenon. In the North East United States Northern Leopard frogs (Rana pipiens) are disappearing from many habitats where they used to flourish. Environmental acidification has been considered as a possible contributor to this disappearance. Therefore, we have focused our research on the effect of this chemical pollutant on aquatic ecosystems, and on the innate immune response of Rana pipiens. Agricultural herbicides and pesticides are another form of chemical pollution. Atrazine is one of the most heavily used agricultural herbicides in the United States and can reach high levels both in aquatic ecosystems as well as in precipitation. Atrazine has been shown to cause demasculinization in frogs during their development both pre and post hatching. Atrazine is known to be a severe endocrine disruptor that promotes the conversion of testosterone to estrogen. We hypothesized that it may also be involved in disruption of normal immune system function, similar to the effect of mild acid exposure on the innate immune response of Northern Leopard frogs. Therefore, we conducted an exploratory study with a single high dose of atrazine (21 ppb) and demonstrated that suggested indeed atrazine functions not only as an endocrine disruptor but also as an immune disruptor (SETAC Globe 2004). Subsequently we demonstrated that this immune suppression occurs in a dose response fashion at the same low concentrations that atrazine disrupts immune function (ETC 2007). Interestingly this response to atrazine may be non-monotonic and we are currently investigating this possibility.