We review the thermal characteristics of all-metallic sandwich structures with two dimensional prismatic and truss cores. Results are presented based on measurements in conjunction with analytical modeling and numerical simulation. The periodic nature of these core structures allows derivation of the macroscopic quantities of interest-namely, the overall Nusselt number and friction factor-by means of correlations derived at the unit cell level. A fin analogy model is used to bridge length scales. Various measurements and simulations are used to examine the robustness of this approach and the limitations discussed. Topological preferences are addressed in terms scaling relations obtained with three dimensionless parameters-friction factor, Nusselt number and Reynolds number-expressed both at the panel and the cell levels. Countervailing influences of topology on the Nusselt number and friction factor are found. Case studies are presented to illustrate that the topology preference is highly application dependent. (c) 2005 Elsevier Ltd. All rights reserved.