Recently, many full-sized keyboards have been designed to fold in various ways in an attempt to make them more transportable. The flexible membrane keyboard, one type of full sized keyboard, is unique because it is made from silicon rubber, thus it is fully flexible and water resistant. Although a number of flexible keyboard characteristics are the same as standard keyboards (i.e. key size, shape and spacing), key-switch and key clicking mechanisms are inherently different. Since there is little or no existing research on flexible keyboards, there is a current need for data to facilitate design of such keyboards for use. Typing performance and perceived usability of several flexible keyboards that differed in terms of material hardness (hard, medium, or soft) and key contact point shape (circular or square) were studied. The results supported the hypothesis that both typing performance and usability of the flexible membrane keyboard were affected by material hardness and contact point shape. Square shaped contact points led to increased typing speed and decreased error rates, and medium or soft hardness led to increased typing speed. The best flexible keyboard (perceived by participants) in general received neutral usability ratings. However, ratings for mobility and design were much higher than neutral. Overall, subjective and objective measures of performance and usability indicated that flexible keyboards that are made of silicon of a soft or medium hardness and with a square shaped contact points are preferred. / Master of Science