The elderly population grows in Brazil and this fact increases the need to develop appropriate information and communication technologies to the public. As cell phones are getting cheaper, many families would like their elderly to be users of these devices aiming to have contact with them when they are out of their homes. However, the current cell phones design favors the younger people, not considering the different needs of the elderly population. At the most, even in the elderly population, there are differences regarding education, experience with technology, cognitive abilities and physical prowess. This dissertation argues for the design, implementation and evaluation of interfaces that are flexible to meet the diverse requirements of the elderly in the interaction with cell phones. One approach to the design of flexible user interfaces was applied in a case study and, considering the results of a practice with elderly users, a set of norms which define the design of the system flexible behavior was specified. This dissertation proposes and presents a framework that provides the interface reconfiguration during the interaction time, named FlexInterface. This framework addresses the concept of interface elements as components that are loaded, instantiated and destroyed when requested. Furthermore, this dissertation also brings an approachthat supports the evaluation of flexible interfaces for the elderly in mobile phones. The proposed analytical approach presents heuristics for this specific context of use. Finally, an assessment with elderly people was performed to verify the feasibility of the proposal. This study found that there was a reduction in the interaction time with the use of flexible interface and an increase in the users' satisfaction.