The subacute dietary (LC50) toxicity of a pesticide as prescribed by the Federal Insecticide Fungicide and Rodenticide Act and of toxic substances as defined by the Toxic Substances Control Act is a routine data point for many chemicals. The methods under which the LC50 data are generated are quite specific and prescribed by law. The dietary toxicity of a chemical is one of the fundamental parameters required by toxicologists in evaluating chemical hazard since dietary exposure is the most probable route of intoxication confronting wild species. The protocol is not designed to mimic a natural situation but to assess the impact on the most vulnerable individuals (juveniles) in a reproducible fashion. In developing the test protocol it was recognized that additives may be necessary to insure uniform distribution on the test chemical in the feed. This study is a pilot effort to address the question of effect of different carriers on dietary toxicity of a particular chemical. The test chemicals were carbofuran, dursban, and endrin--representing the general pesticide classes of carbamates, organophosphates and organochlorine insecticides, respectively. The carriers that were evaluated include table grade corn oil, propylene glycol, carboxy methylcelluose and distilled water.