In this paper we propose a novel approach for the thermal conductivity determination in thermal membrane-based devices. In the presented methodology, the fitting of experimental and simulated thermal dissipation of two resistive elements is used to characterize both the materials composing the membrane structure and the material used in the heating element patterning. The determination of this parameter, usually disregarded in most of the analysis, leads to a complete characterization of the structure and represents an improvement, as a better accuracy in the thermal properties of the membrane under study can be achieved. To demonstrate its effectiveness, the method has been applied to a already-fabricated flow sensor structure. (c) 2005 Elsevier B.V. All rights reserved.