Electrochemical measurement of mass transfer enhancement in a dilute suspension of particles, due to particle rotation in the presence of a shear flow, has been studied with a Couette cell. An effective diffusivityDe involving the Peclet numberPe of the particles and the molecular diffusivityD of the solute was obtained for low particle volume fraction ϕ asDe=D(1+3.5ϕPe1/2). From steady-state and transient data, it was shown that aggregation may occur with alumina particles and that inertial effects due to centrifugation reveal a marginal layer free of particles near the rotating inner cylinder.