Under a jointly sponsored Army/NASA contract NAS1-13479 (Army Structures Laboratory, USARTL (AVRADCOM), and NASA-Langley) Sikorsky Aircraft has been conducting programs for the design, fabrication and test of advanced composite airframe structures. This paper will present the progress of Phave IV of the contract involving cabin roof structures.The cabin roof structure is one of the most complex regions in an all composite helicopter airframe. The roof contains highly loaded joints where the major frames and beams intersect and high concentrated loads from the main gear box are introduced. Under Phase IV the design of a roof structure has been completed which consists of all graphite/epoxy structural elements bonded as an assembly without any mechanical fasteners. Fabrication used aluminum tooling with control on all mating surfaces to provide accurate bondlines. The results of static tests are presented. Program results have verified a twenty-six percent weight saving from the current production metal baseline. The purpose of this paper is to present the latest progress in the development of all composite helicopter airframe structures.