In order to estimate the environmental risk of the use of Alachlor, experiments on laboratory animals were conducted. Alachlor and 2,6 diethylaniline content in blood serum was quantified. Three groups of male ACI/T rats and C3H/FEJ mice were treated with three different doses of Alachlor. Six hours after the intraperitoneal injection the animals were bled and blood was collected by cardiac puncture. From serum obtained after blood centrifugation, A and DEA were extracted using diethyl ether. 2,6 diethylaniline and Alachlor determinations were carried out by high performance liquid chromatography (HPLC). The HPLC revealed that the metabolic capacity of 2,6 diethylaniline production from Alachlor in rats is dose-dependent; moreover, the animals can be subdivided into at least two groups, according to their Alachlor metabolic capacities. In mice the metabolic release of 2,6 diethylaniline was found to be practically complete at every dose tested.