In this work, acrylic acid grafted PTFE fibers were prepared as a new packing material for flow injection (FI) on-line microcolumn preconcentration coupled with flame atomic absorption spectrometry (FAAS) for determination of trace lead and cadmium in environmental and biological samples. Effective preconcentration of trace cadmium and lead was achieved in a pH range of 3.5-6.5 on a microcolumn packed with the developed new packing material. The retained lead and cadmium were efficiently eluted, respectively, with 1.0mol/l HNO3 and 0.5mol/l HCl for on-line FAAS determination. The developed sorbent exhibited fairly fast kinetics for the adsorption of Pb (II) and Cd (II), permitting the use of high sample flow rates up to at least 10.8ml/min for the FI on-line microcolumn preconcentration system without loss of the retention efficiency. With a preconcentration time of 45 s at a sample loading flow rate of 10ml/min, the enhancement factor was found to be 49 for Pb and 73 for Cd at a sample throughput of 55h−1. The detection limits (3σ) was 0.26 and 0.10μg/l for Pb and Cd, respectively. The precision (RSD) for 11 replicate measurements was 1.9% at the 25μg/l Pb level, and 0.9% at the 10μg/l Cd level. The developed method was successfully applied to the determination of trace Pb and Cd in a variety of environmental and biological samples.