This work elucidated the effects of liquid subcooling on the relative stability between nucleate boiling and film boiling on an inclined surface. At each heater＇s orientation and liquid subcooling of 0-20 K, the co-existing heat fluxes were found, from which the equilibrium heat flux (q(c)) was identified. Experimental results indicate that q(c) increases with liquid subcooling, with the maximum q(c) occurring at rotating the surface by 90 degrees from the horizontal position. In addition, equal-area criterion was adopted to properly interpret the experimental results. The shift in transition boiling curve correlated well with the change in relative stability when varying the heater orientation and liquid subcooling. (C) 2000 Elsevier Science Ltd. All rights reserved.