An on-line system for preconcentration and determination of lead at mu g L-1 level is proposed. Amberlite XAD-2 functionalized with 2-(2'-benzothiazolylazo)-p-cresol (BTAC-XAD) packed in a minicolumn was used as sorbent. Chemical and hydrodynamic variables were evaluated and the results demonstrated that lead can be determined using sample pH at 7.0-7.5, elution with 0.050 mol L-1 HCI and a sample flow rate of 6.0 mL min(-1). Enrichment factors of 19, 43, and 60 were achieved by using the time-based technique with preconcentration periods of 60, 120, and 180 s, respectively. Detection limit (3s) was 1.7 mu g L-1 when used preconcentration time of 180 s. This procedure was applied to lead determination in natural water samples. Accuracy of procedure was confirmed by lead determination in certified reference materials.