The determination of trace and ultra-trace concentrations of vanadium(V) by adsorptive cathodic stripping voltammetry on a glassy carbon mercury film electrode is described. The method involves a controlled preconcentration of the element by interfacial accumulation as vanadium-pyrogallol complex on the electrode followed by cathodic stripping voltammetric measurement. The optimum analytical conditions for the measurement of vanadium by this method include the use of 0.20 M acetate buffer at pH 5.6 to 5.8, 5 × 10-4 M pyrogallol, an accumulation potential of -0.30 V vs. Ag/AgCl and a rotated electrode at 1920 rpm. The study of inorganic interference indicated that metal ions generally do not interfere with the vanadium determination, except for Pb(II) ions. However, the effect of this interference is eliminated by the addition of EDTA into the solution. The interference of surface-active substances, e.g., Triton X-100, is overcome by UV irradiation of the sample. For a 3-min accumulation, the linear concentration range obtained is 0-75 μg l-1 (R2 = 0.948) and lowest detectable amount is 1.0 μg l-1 (R.S.D. = 9.5%). The use of the adsorptive voltammetric technique after dry-ashing and UV treatment of the samples is successfully demonstrated for the determination of vanadium in standard biological and environmental reference materials.