Urine samples (24 h) were collected from the rice farmers before and post insecticide application. Samples were analysed for 3,5,6-trichloropyridinol (TCP), the major urinary metabolite of chlorpyrifos, using an enzymatic pre-treatment before extraction followed by HPLC–MS/MS. Absorbed Daily Dose (ADD) of chlorpyrifos for farmers were then estimated from urinary TCP levels, expressed as μg g−1 creatinine. The analytical method for urinary TCP had a low detection limit (0.6 μg L−1), acceptable recovery values (80–114%), and low relative percentage differences in duplicate and repeated samples