A new and efficient numerical procedure is applied for the inverse simultaneous estimation of temperature-dependent thermal properties (thermal conductivity and volumetric heat capacity) of fully developed fluids flowing through a circular duct. The procedure makes use of both the Sequential Function Specification Method as the inverse protocol and the Network Simulation Method as the numerical technique. The temperature solution at discrete times at several points of the wall-fluid interface can be solved from the direct problem by adding a normal random error. A time-dependent heat flux boundary condition is applied to the inlet region. The proposed method provides estimations of the functions, k(T) and C(T), regardless the waveform of those functions even without prior information on the kind of dependence concerned. The solutions take the form of piece-wise functions with a number of stretches that may be specified. A common iterative least-squares approach is used to minimize the classical functional. Various approaches to solving this problem are discussed. (C) 2007 Elsevier Ltd. All rights reserved.