The thermal and hydrodynamic characteristics of a heat sink formed of a fractal channel network are analyzed and compared with those of a heat sink formed of a classical parallel channel network. The analysis covers laminar and turbulent flow regimes in both macro and microchannels.. with emphasis on the latter. Reynolds number dependence of the thermal and hydrodynamic characteristics of the channel flow is considered. It is shown that employing a fractal microchannel network in a heat sink does not improve thermal performance relative to that of a heat sink formed of a parallel microchannel network. On the other hand, the hydrodynamic performance of the heat sink with the fractal microchannel network is increased for turbulent flow and decreased for laminar flow relative to that of the heat sink with the paraflel microchannel network. (C) 2004 Elsevier Ltd. All rights reserved.