An experimental investigation addressing the effect of the release of dissolved noncondensables on the heat transfer in a long, heated microchannel subject to subcooled liquid forced convection was conducted. The convection heat transfer coefficients near the exit of a copper microchannel with 0.76 mm inner diameter and 16 cm heated length, subject to forced-flow cooling by subcooled water, were measured. The range of experimental parameters were: wall heat flux = 0.5-2.5 MW/m(2); liquid velocity = 2.07 to 8.53 m/s; channel exit pressure = 5.9 bar. Experiments were performed with degassed water and water saturated with air. The convection heat transfer coefficients obtained with degassed water were systematically under predicted by the widely-used Dittus-Boelter correlation for turbulent pipe flow. The presence of dissolved air in water could increase the heat transfer coefficients by as much as 17%, despite the fact that the maximum increase in the coolant velocity due to the noncondensable gas release was only a few percent. The heat transfer enhancement increased with increasing the heat flux and decreasing the liquid velocity.