Preparations containing both organophosphates and pyrethroids are commonly used in insect control. Toxicokinetic interactions between α-Cypermethrin (CM ) and Chlorpyrifos (CPF) were studied in rats. The animals were given a solution of CM or CPF in rapeseed oil at a dose of 10 mg/kg and a mixture of CM and CPF at a dose of 5 mg/kg each by an intragastric tube once a day for 28 days. The concentrations of unchanged CM and CPF were determined in blood, liver and brain by GC-ECD. Also, the concentrations of CM and CPF were individually monitored in blood after administration of their single doses to calculate toxicokinetic parameters (T_max., C_max., AUC). In urine the main metabolites 3-(4^’-hydroxyphenoxy)benzoic acid (4OH₃PBA) and 3,5,6-trichloro-2-pyridinol (TCP) were determined by HPLC in the rats treated daily with CM , CPF or their mixture. In the animals dosed with a single insecticide, the highest concentration of CM was found in blood and of CPF in liver. In the co-exposed rats, CPF decreased in all the tissues, while CM increased particularly in liver. The excretion of 4OH₃PBA following CM administration increased significantly during the exposure period, whereas in the CPF-exposed rats, TCP was excreted at the same rate. Following the co-administration of both insecticides 4OH₃PBA excretion decreased, but did not influence TCP excretion. In the coexposed animals, C_max. and AUC increased for CM, and decreased for CPF.