A study of the stability of an electrically heated, forced-convection, single horizontal channel system with a gas-loaded surge tank placed upstream of the heated channel was conducted. Freon 11 was used as the test fluid. The major modes of oscillations, namely, density wave-type (high-frequency) and pressure drop-type (low-frequency) oscillations, have been observed. Steady-state pressure drops, stable and unstable boundaries are experimentally determined for given ranges of heat flux, mass flow rate, and compressible volume in the surge tank.