The issues surrounding inerts testing have become some of the highest profile issues affecting pesticide formulations today. Most agree that the Environmental Protection Agency (EPA) has been correctly concerned about the lack of toxicity data for various inert components used in pesticide formulations. In many cases this concern is justified; however, in an equal number of cases, a great deal of data exists which needs to be provided to EPA in an orderly manner. This will enable suppliers to assure formulators of a continuing supply of acceptable inert materials for their future use. The following discussion will focus on several aspects of the regulations which have become apparent as the industry moves forward in understanding and implementing the new pesticide procedures. These aspects include testing requirements, animal considerations, and state versus federal requirements.