Evidence that amphibian deformities are on the rise has prompted a number of researchers to question a variety of natural and man-made substances, including chemicals such as s-methoprene (trademark Altosid), an insect growth regulator applied to water bodies for mosquito control. Despite conclusions reached by the U.S. Environmental Protection Agency and a considerable body of scientific evidence demonstrating that it is unlikely that s-methoprene or any of its degradation products are causing the high rates of deformities found in Minnesota and other states, concerns persist about potential negative impacts of s-methoprene on nontarget species, specifically anurans. Water analyses in field and laboratory conditions and a comparison of reported Altosid use with reported frog deformities in Minnesota demonstrate that a connection between frog deformities and Altosid use is unlikely. These results indicate that factors other than s-methoprene and its degradation products are contributing to the recent outbreak of frog deformities.