Following an analysis of surface roughness features that develop on a 3D C/C composite during ablation, i.e. wall recession by oxidation and/or sublimation, a modeling strategy is set up in order to predict the composite behavior from that of its components. it relies on two changes of scale: (i) microscopic scale (fiber, matrix) to mesoscopic scale (bundle) and (ii) mesoscopic scale (bundle, matrix) to macroscopic scale (composite). The physical basis is a general model for receding surfaces under a gasification process coupled to mass transfer. At each scale, the 3D surface equation is analytically solved in steady state considering a 1-D mass transfer perpendicular to the overall surface. The models are validated by comparison to experimental data. (c) 2008 Elsevier Ltd. All rights reserved.