Technical Abstract: The effect of fourteen microbial inoculants on the fermentation and nutritive value of alfalfa silages was studied under laboratory conditions. First (477 g dry matter (DM)/kg) and second cuttings (393 g DM /kg) of a second year alfalfa stand were ensiled in two experiments. In both experiments, alfalfa was harvested with standard field equipment. All inoculants were applied at 10^6 colony-forming units (cfu)/g crop. Uninoculated silages served as controls. After treatment, the chopped forages were ensiled in 1.0 and 0.5-L anaerobic glass jars, respectively, at a density of 500 g/L. Each experiment had fifteen treatments (uninoculated control and fourteen inoculants), four silos per treatment. Silos were stored for a minimum of 30 days at room temperature (~22 C). In first cut, all inoculants but one reduced pH relative to the uninoculated control, and all but two of the homofermentative strains shifted fermentation toward lactic acid. In second cut, the epiphytic lactic acid bacteria population was 2.7 x 10^7 cfu/g, and only commercial inoculants produced significant shifts in fermentation. In spite of the positive effects on silage fermentation, 48-h in vitro true digestibility was not improved by inoculation with lactic acid bacteria.