This paper reports an electrochemical study of local mass transfer behaviour in decaying annular swirl flow. Initially, flow visualisation experiments were conducted to observe the general behaviour of the flow. It was found that the swirl angle decays exponentially along the tube. Measurements of pressure drop across the vaned swirl generators were correlated in terms of the inverse of the square of the tangent of the vane angle and approximately the square of the mean fluid velocity for vane angles of 30-degrees and over. Measurements of the axial distribution of local mass transfer coefficient for the inner rod were carried out using the electrochemical limiting diffusion current technique and results were correlated for each swirl generator, in the Reynolds number range 3300-50000. It was found that the relative enhancement of mass transfer in swirl flow increases as the vane angle increases and Reynolds number decreases.