An experimental investigation into the effects of transverse oscillations on the heat transfer from a circular cylinder in cross-flow was carried out. The cylinder's heat transfer coefficient was measured for a wide range of oscillation frequencies and amplitudes. Heat transfer enhancement was found to be strongly dependent on synchronization with harmonics of the natural shedding frequency, the cylinder wake mode, and the cylinder transverse velocity. For representative oscillation conditions, the velocity and temperature fields in the near wake were measured using digital particle image thermometry and velocimetry (DPIT/V). This revealed several mechanisms that explain the observed heat transfer enhancement. (c) 2006 Elsevier Ltd. All rights reserved.