A new method for the determination of paraquat in biological fluids has been developed. It involves thin-layer chromatography with flame ionization detection (TLC/FID) and simple solid-phase extraction with a disposable octadecylsilane column. This procedure allows direct loading of the samples on the disposable column. When Chromarod SII is used as the stationary phase and methanol-2N hydrochloric acid (2:3, v/v) as the mobile phase, recovery levels of paraquat in spiked materials are from 87.5 to 98.0%. This method can be used for samples of paraquat at levels as low as 50 ng.