The crystallization behavior of nylon-6 confined in a hybrid of nylon-6 and ultra-fine full-vulcanized powdered rubber was studied. It is found that carboxylic styrene-butadiene ultra-fine full-vulcanized powdered rubber (CSB-UFPR) could behave as a nucleating agent for nylon-6 crystallization, which can increase the crystallization temperature, the onset temperature of crystallization as well as the glass transition temperature of nylon-6 confined in the hybrid of nylon-6 and ultra-fine full-vulcanized powdered rubber. It is also found that nylon-6 molecules confined among CSB-UFPR particles favor the crystalline form of gamma than that of alpha. The crystallization process of gamma phase of nylon-6 in nylon-6/CSB-UFPR hybrid is a diffusion-controlled process, and thus it can be accelerated by raising the crystallization temperature or by extending oil into CSB-UFPR. It is expected that these results will benefit the research on crystallization behavior of other constrained geometry polymer, such as ultra-thin film and polymer/clay hybrid, and etc. (C) 2004 Elsevier Ltd. All rights reserved.