Heat transfer performances for non-boiling and boiling flow of a micro-vaporizer have been measured by standard methods (temperatures, flow rates, effective power input). The study was carried out for laminar flow (Re < 25) in silicon micro-channels (5 mm x 3 cm x 200 mum) filled with ordered obstacles to increase the specific area. The results obtained show a strong dependence of the heat transfer on the Reynolds number for the non-boiling flow and pretty high heat transfer coefficients (1300-2500 W/m(2) K) for the boiling flow. Image analysis was introduced to estimate the volume vapour fraction, which can be converted into the mass vapour fraction using the slip ratio. The estimation of this slip ratio is discussed in this paper. (C) 2004 Elsevier B.V. All rights reserved.