Unsteady conjugate heat/mass transfer between a circular cylinder and a surrounding fluid flow has been analysed. Numerical investigations were carried out for the cylinder Reynolds numbers equal to 2 and 20 and different values of the Prandtl/Schmidt numbers. The heat/mass balance equations were solved numerically in cylindrical coordinates by the ADI finite difference method. The computations yield information regarding the influence of the parameters that characterize the coupling features of the conjugate heat/mass transfer, i.e. the physical properties ratios, on Nusselt/Sherwood numbers and cylinder dimensionless average temperature/concentration. The thermal/mass wake phenomenon were also studied. (C) 2003 Elsevier Ltd. All rights reserved.