Information appliances such as notebook computers and cellular telephones are becoming integral to the lives of many. These devices facilitate a variety of communication tasks, and are used for employment, education, and entertainment. Those with disabilities, however, have limited access to these devices, due in part to product designs that do not consider their special needs. A usability evaluation can help identify the needs and difficulties those with disabilities have when using a product and universal design principles can then be applied to enhance accessibility and usability. This study addresses the usability of two of the most common information appliances - notebook computers and cellular telephones. The usability of notebook computers was evaluated using a remote ethnographic method where participants recorded usability-related critical incidents. Participants included those with a wide range of abilities, such as legal blindness, total blindness, and upper extremity physical disabilities. Objective and subjective measures were used to determine the effects of several specific design parameters for cellular telephones. The notebook computer study revealed that participants have difficulty with non-standard keyboard layouts, the use of isometric pointing devices, case latches, and inadequate system feedback. User performance and ratings in the cellular telephone study were the best with the 12 mm lateral pitch and 0.7 mm key height, while the fewest task failures were committed using the 0.5 mm keystroke. Participants also preferred telephone models with large <Power>, <Send> and <End> keys located in prominent locations, and 22-point and 36-point display fonts. These results were used to generate product-specific design guidelines that can be used to design notebook computers and cellular telephones that are more usable and accessible for users with visual and upper extremity physical disabilities. Universal design implications are also discussed. / Master of Science