Reintroducing crop diversity and reducing external inputs are important initial steps to a more sustainable agriculture. The role of functional diversity was explored in an annual forage intercropping system. Four warm-season, drought-tolerant annual forage crops were evaluated for use in the Northeast United States. The species had two different functional traits, stature and nitrogen acquisition traits: 1) cowpea (Vigna unguiculata L., legume, short); 2) sunn hemp (Crotolaria juncea L., legume, tall); 3) pearl millet (Pennisetum glaucum L., grass, short); and 4) sorghum sudangrass (Sorghum bicolor L. Moench x S. sudanense P., grass, tall) and were seeded in monocultures and in three and four species intercrops. Crop and weed biomass were sampled twice by clipping vegetation in 0.5 m2 area at approximately 45 and 90 days after planting (DAP). When averaged across site-years, crop biomass and crop growth rate of legume monocultures were lower than other treatments at both sampling times. Biomass for the monocultures at the second sampling date ranged from 2,500 kg ha-1 (cowpea) to 9,300 kg ha-1 (pearl millet). No biomass differences were found between the intercrops and grass monocultures, which ranged from 7,800 to 9,600 kg ha-1. Although the intercrop treatments did not produce more biomass than the two grass monoculture treatments, all intercrops had land equivalent ratios (LER) greater than 1. Grasses and intercrop treatments were similarly weed suppressive. The pearl millet-sorghum sudangrass-sunn hemp intercrop consistently produced the most biomass, but not significantly more than the pearl millet monoculture, which had a much lower seed cost. Therefore other potential benefits of summer annual forage intercrops (e.g. improved forage quality and increased soil health) must be considered to justify the increased seed costs. v