Hair analysis for dialkyl phosphates' (DAPs) residues could provide a measure of chronic exposure to organophosphate pesticides (OPs). The aim of this study was to determine whether these metabolites can be internally incorporated into the hair of rabbits exposed to dimethoate and also to investigate the influence of dose and dose duration of this OP, as well as the effect of hair colour on the concentrations of its DAPs in hair. Two-coloured rabbits were daily exposed to dimethoate (0, 12 or 24mgkg(-1) body weight) via their drinking water. Hair samples of both colours were obtained 4 and 6 months after the beginning of exposure from the back of all treated rabbits, and each hair colour sample was analyzed for dimethyl phosphate (DMP) and dimethyl thiophosphate (DMTP) by gas chromatography-mass spectrometry (GC-MS). Analysis revealed the incorporation of these metabolites into the rabbit hair in a dose-dependent manner. The mean concentrations found ranged from 0.18 to 0.77ngmg(-1) for DMP and from 0.43 to 1.53ngmg(-1) for DMTP. Mixed results for the significance of the relationship between dose duration and the levels of the two DAPs in hair are observed. Hair pigmentation does not appear to affect the concentration values of DMTP, whereas it seems to be a critical factor in the incorporation of DMP into hair. These data confirm the ability of hair testing to assess chronic OP exposure by the detection of DAPs.