Aquisition of data on the long-term behavior of composite pressure vessels is costly, not only for materials but also for fabrication and testing. If proven accurate, one way to minimize cost is to extrapolate the vessel performance from the strand data. We at the Lawrence Livermore Laboratory (under joint contract with NASA-Lewis Research Center) have been conducting stress-rupture tests on epoxy-impregnated strands and composite pressure vessels. We have accumulated 7 y of lifetime data on strand specimens and vessels have been held under constant pressure for over 1 y.