This paper investigates the mechanism of vapor-film collapse by a propagative collapse for film boiling at high wall-superheat. It also reports effects of a local-cold spot on both the minimum-heat-flux (MHF) temperature and the way in which the vapor film would collapse. Experimental results showed that propagation velocity of vapor-film collapse would decrease and MHF temperature would increase when the local-cold spot temperature was decreased. The results also showed that the MHF temperature increased remarkably when the local-cold spot temperature was lower than the thermodynamic limit of liquid superheat, T-tls. It was proved through analytical and numerical models that local temperature at the collapse front of the vapor film, namely the local solid surface temperature at the position of liquid-solid contact, could never exceed the T-tls even if the vapor-film collapse occurred at a high wall-superheat. (C) 2003 Elsevier Ltd. All rights reserved.