Carbon fiber/epoxy laminates containing three different types of rubber modifiers, separately and in combination, were developed for testing in a cryogenic environment. Preformed rubber particles, core shell rubber, and solid carboxyl-functionalized rubber were chosen as additives to a model prepreg matrix to control the placement of the rubber within the resulting laminates. Cryogenic microcracking and mode I and II fracture toughness and interlaminar shear strength experiments were performed. Scanning electron microscopy was used to observe fracture surfaces of the rubber-modified laminates. Fracture toughness properties were improved while the ILSS decreased because of the presence of these rubber modifiers. It was observed that the presence of these modifiers significantly reduced the microcrack density of the laminates exposed to cryogenic cycling, and in the case of one, even eliminated microcracking entirely. (C) 2003 Wiley Periodicals, Inc.