Alfalfa (Medicago sativa L.), cultivars ARC, Regen Y and Saranac were selected in vitro in a recently developed acid/aluminum toxic media. The new media produced higher initiation rates and higher fresh callus weights than those obtainable with the media described by Meredith and Connor for the selection of aluminum resistant variants in Nicotiana plumbaginofolia. Both rescue and direct initiation yielded adequate amounts of healthy callus for the initiation of embryogenesis. The toxic effect of the acid/aluminum media is expressed in both the percent of explants initiating callus and in the fresh-weights obtained during initiation and two subsequent subcultures.