In comparison with the conventional foaming process, microcellular foaming by injection molding has the advantage of forming small bubbles of consistent size. Because of the reduction in the cycle time, the removal of sink marks, scale reliability, and weight lightening, microcellular foaming by injection molding is widely applied to electrical products, such as automotive parts, office automation equipment, and laptops. When microcellular foaming by injection molding is used with a resin such as polycarbonate, acrylonitrile butadiene styrene, or PC/ABS, micro-bubbles form. This enables the manufacture of cell phones, notebooks, and personal digital assistants (PDAs), which are impossible to produce with the conventional foaming technique because these products require a thin wall. For most thin-wall products, spray and labeling processes are added. Therefore, research into the spray and labeling characteristics of injected foamed parts should come before applications. In this article, we analyze the swelling phenomenon that results from labeling on microcellular foamed parts. (c) 2005 Wiley Periodicals, Inc.