Advanced fibrous reinforced composite materials make available to the aircraft industry the potential for substantial structural weight savings. These savings will be realized only after a general industry- wide understanding and acceptance of these unique materials has been established. A logical initial step involves the formulation of a design approach consistent with the requirements of minimum weight, cost effectiveness and reliability inherent in the design of aircraft structures. This design approach indicates that initial aircraft structural applications will be basically unidirectional, minimize attachment problems, allow secondary loads to be carried by conventional isotropic structural materials, and will allow for reasonable analysis capability and fabrication simplicity. A com posite beam designed to meet the requirements of a typical Boeing 707 floor beam has been evaluated in order to demonstrate this proposed design approach.