Chain scission was observed during the crystallization of p-xylene in dilute polystyrene solutions. Degradation yields were determined by gel permeation chromatography, as a function of the number of freeze-and-thaw cycles, polymer concentration, and initial polymer molecular weight (M). The rate constant for chain scission K(c) increases with the polymer chain length, from 0.021 % /cycle at M = 110 . 10(3) to 4.7% /cycle at M = 8.5 . 10(6). Over the two decades range of investigated molecular weights, K(c) follows an empirical scaling law of the form K(c) approximately (M - M(lim))1.17, where M(lim) is a limiting molecular weight congruent-to 29,000 g . mol-1 below which no degradation could be induced. Some propensity for midchain scission was detected, although this tendency was much weaker in comparison to flow-induced degradation. A chain scission model based on crack propagation failed to reproduce the experimental results. To explain the observed dependence of K(c) with the square of the radius of gyration, an interfacial stress transmission mechanism between the crystallization fronts and the polymer coil has been proposed.