The application of capillary ion electrophoresis to the separation and determination of chromium (VI), molybdenum (VI) and vanadium (V) with direct on-column UV detection at 254 nm is described. Using a cathodic injection and anodic detection scheme, Cr(VI), Mo(VI) and V(V) were separated in about 4 min in a fused silica capillary column, with a phosphate buffer of pH 12.0, at an applied voltage of 15 KV, followed by direct UV detection. An electro-osmotic flow modifier, namely a cetyltrimethylammonium bromide (CTAB), is necessary to shorten the migration times of these ions. Incorporating citrate into the electrophoretic buffer markedly improves the sensitivity and efficiency.