In contrast to overwintering cold hardening, a rapid cold hardening process has recently been described in insects. Thisprocess can rapidly enhance cold tolerance of insects in several hours or even minutes. The characteristics of rapid cold hardening includeinducing conditions, cold hardening effects, and fitness costs. Physiological and biochemical mechanisms of rapid cold hardening includerapid changes in the phospholipid composition and the increase in hemolymph osmolalities, polyols production, proline and cold-inducedproteins. Moreover, there are different views about the ecologically adaptive significance of rapid cold hardening in insects. This paper re-views research results about rapid cold hardening of insects since 1987, focusing on forms of cold injury, strategies of cold tolerance, anddefinitions, characteristics, physiological and biochemical mechanisms and adaptive significance of rapid cold hardening. In contrast to overwintering cold hardening, a rapid cold hardening process has recently been described in insects. This process of rapidly enhance cold tolerance of insects in several hours or even minutes. The characteristics of rapid cold hardening include induction conditions, cold hardening effects, and fitness costs . Physiological and biochemical mechanisms of rapid cold hardening includerapid changes in the phospholipid composition and the increase in hemolymph osmolalities, polyols production, proline and cold-inducedproteins. Moreover, there are different views about the ecologically adaptive significance of rapid cold hardening in insects. This paper re-views research results about rapid cold hardening of insects since 1987, focusing on forms of cold injury, strategies of cold tolerance, anddefinitions, characteristics, physiological and biochemical mechanisms and adaptive significance of rapid cold hardening.