A simple on-line separation/preconcentration procedure is described for the determination of trace levels of Pb(II) by flame atomic absorption spectrometry (FAAS). A mini-column packed with Dowex Marathon C (DMC) ion-exchange resin was used for the on-line preconcentration of Pb(II) at pH 3.5. Pb(II) was sorbed on the resin, from which it could be eluted with 3 mol L-1 HCl and then introduced directly to the nebulizer-burner system of FAAS. The parameters influential on the determination of Pb(II) ions such as the pH of sample solution, eluent type, interfering ions and flow variables were studied. Under the optimum conditions, the calibration graph obtained was linear over the concentration range of 0.01-0.1 mg L-1. The detection limit of the method was 1.3 mu g L-1 while precision was 1.1% (n = 15) at a 0.05 mg L-1 Pb(II) level. The accuracy of the method was proven using standard reference materials. The developed method has been applied successfully to the determination of lead in water and various environmental samples with satisfactory results.