Technical Abstract: Longer term persistence and sustained biomass yields of alfalfa (M. sativa) stands are important for producers. Yield performance and persistence of intrasubspecific crosses between alfalfa subsp. sativa and falcata after the first post-establishment year are unknown. The objectives of this study were to measure biomass yields, persistence, and biomass yield stability in inter and intrasubspecific alfalfa crosses. Nine elite sativa clones and five falcata clones were crossed in a diallel mating design. Progeny were space planted in 1998 at Ames and Nashua, IA and evaluated for persistence, biomass yield, and biomass yield stability from 1998 through 2002. Sativa by falcata hybrids produced substantial biomass yield and exhibited heterosis through the first post-establishment year, but declined in subsequent years. During that period, intersubspecific hybrids were equivalent to the more persistent hybrids derived from crosses among sativa genotypes; however, the hybrid persistence levels declined somewhat in relation to the sativa crosses in later years. Surprisingly, intrasubspecific hybrids had less biomass yield stability than the more stable intrasubspecific sativa crosses. Selection of improved falcata germplasm for long term persistence and higher yield is needed.