The subject of the present work is a multidimensional modelling of vertical upward subcooled boiling flow using a two-fluid approach and calculation of local two-phase flow parameters (void fraction and bubble size). The dependence of bubble diameter on local flow conditions was taken into account. A sensitivity analysis of closure equations showed that besides phase-change mechanisms, the transverse hydrodynamic mechanisms also have to be considered for modelling of subcooled flow boiling at low-pressure conditions. The evolution of cross-sectional distributions of void fraction and local bubble diameter along the flow was simulated and compared to low-pressure experimental data from the literature [Experimental investigation of subcooled boiling, M.S.N.E. Thesis, Purdue University, West Lafayette, IN. USA, 1999; Int. J. Multiphase Flow 28 (2002) 1351]. (C) 2003 Elsevier Ltd. All rights reserved.