Flow injection analysis with amperometric detection (FIA-AD) at screen-printed carbon electrodes (SPCEs) in optimum medium of Britton-Robinson buffer (0.04molL(-1), pH2.0) was used for the determination of three tumor biomarkers (homovanillic acid (HVA), vanillylmandelic acid (VMA), and 5-hydroxyindole-3-acetic acid (5-HIAA)). Dependences of the peak current on the concentration of biomarkers were linear in the whole tested concentration range from 0.05 to 100molL(-1), with limits of detection (LODs) of 0.065molL(-1) for HVA, 0.053molL(-1) for VMA, and 0.033molL(-1) for 5-HIAA (calculated from peak heights), and 0.024molL(-1) for HVA, 0.020molL(-1) for VMA, and 0.012molL(-1) for 5-HIAA (calculated from peak areas), respectively.