A procedure is described for the determination of molybdenum using square wave catalytic stripping voltammetry in the presence of 2,3-dihydroxynaphthalene (DHN) and bromate. Linear scan voltammetry revealed that Mo(VI) forms a 1:2 complex with DHN and undergoes a one-electron reduction at the hanging mercury drop electrode. This reduction is reversible and especially suitable for square wave voltage modulation. A large enhancement of the peak current (500 X) is observed upon the addition of bromate. The optimum conditions were 1x10(-3) M DHN, 3x10(-2) M bromate, pH4.7, and an adsorption potential of -0.05V. For an adsorption time of 1 min, the relative standard deviation for the measurement of 5x10(-12) M Mo(VI) was +/-4% (n=7), and the detection Limit was determined as 6x10(-12) M. The peak current was linear with the concentration of Mo(VI) from 1x10(-11) to 1x10(-9) M. The linear range could be extended with shorter adsorption times or a non-stirring adsorption mode.