A bead-injection spectroscopy-flow-injection analysis (BIS-FIA) system with spectrophotometric detection has been developed for the determination of cobalt. A homogeneous bead suspension of Dowex 50 W resin (600 microL) previously loaded with the chromogenic reagent 1-(2-pyridylazo)-2-naphthol (PAN) was injected to fill the flow-cell. Co is injected into the carrier (pyrophosphate, pH 5) and reacts with the immobilized chromogenic reagent to form a green chelate. The analytical signal corresponds to the formation of the Co-PAN complex on the solid surface. At the end of the analysis, the beads are discarded by reversing the flow and instantaneously transported out of the system. The sensor shows both excellent selectivity, which could also be increased with a simple on-line modification to avoid interferences from Ni(II), Zn(II) and Cu(II), and good sensitivity; the detection limit was 19 ng mL(-1), the linear range 50-2000 ng mL(-1) and the RSD (%) 4.16. The method was satisfactorily applied to the determination of Co in waters, pharmaceuticals and alloy steels.