In order to investigate dissipation behaviour of malathion, fenitrothion, dimethoate, chlorpyrifos and pirimiphos-ethyl during the infusion process, pesticide-free dried peppermint leaves were spiked with the pesticides. Infusions were prepared according to the usual process of infusion preparation. The effect of the infusion process on the transfer of the pesticides from the spiked peppermint leaves into brew was examined at intervals of 5, 10, 15 and 20 min. Residues were determined using a gas chromatograph equipped with a flame ionisation detector (FID). The decrease in pesticide levels during infusion was found to be statistically significant (P < 0.05). Transfer of residues decreased significantly with infusion time. The carryover of the residues of dimethoate, which has the highest water solubility, into the infusion was the highest. Satisfactory relationships were found between water-solubility (Ws), partition coefficient (K-ow) and Henry's law constant (H) of the pesticides with the transfer of pesticides to brewed tea. It was observed that not only water solubility or K-ow but also H controls the dissipation of the pesticides from water or their air-water partitioning. (c) 2006 Elsevier Ltd. All rights reserved.