Rapid cold hardening (RCH) is a type of phenotypic plasticity in which a short chilling period increases tolerance to normally lethal temperatures. The role of RCH in protecting against lethal temperatures is well-established, but less is known about the effect of RCH in protecting ectotherms at the nonlethal temperatures experienced in the field. To better understand the role of RCH at temperatures commonly experienced in the field, we tested the hypothesis that RCH protects against sublethal cold injury in Drosophila melanogaster. In preliminary experiments we exposed flies to one of three treatments: control (25 for 2 h), direct chilling (-2 for 2 h), or RCH (4 for 1 h followed by -2 for 2 h); the results indicated that nearly 100% of flies survive at -2 degrees Celsius in both direct chilling and RCH treatments. In ongoing experiments, we are testing the ability of RCH to protect against suborganismal cold damage, preserve energy balance, and improve fecundity following cold stress. Together, these experiments will provide a thorough assessment of the ability of RCH to protect against sublethal cold injury.