Heat balance models predict that heat released upon serpentinization of peridotites can result in a wide range of hydrothermal venting temperatures. Temperatures ranging from a few to a few tens of ¿C are likely. Temperatures ~300¿C may be possible in conjunction with significant heat input from below, low fluid flow rate (≤10 kg/s), a high rate of serpentinization (≥100 kg/s), or some combination of these factors. The volume of fresh lithosphere accessible to serpentinization may limit the duration of an episode of hydrothermal venting when the serpentinization rate exceeds 10 kg/s. Hydrothermal venting driven by high rates of serpentinization may occur episodically as new reaction surfaces are made available by tectonic activity or crack propagation. Given the uncertainty of several parameters, the current episode of venting at the Lost City vent field on the Mid-Atlantic Ridge may range from ~102 to 104 years.