Tetraplold alfalfa (Medicago sativa L.) germplasm, in which two‐thirds of the plants are capable of regeneration from callus tissue in culture, has been developed by recurrent selection. It descends from one ‘DuPuits’ and four ‘Saranac’ clones which regenerated in the cycle 0 population. Frequency of regeneration was 12% in cycle 0, about 50% in cycle 1, and 67% in cycle 2. Seed produced by hand‐intercrossing 75 plants regenerated from cycle 2 has been termed ‘Regen‐S’ (Regen for regeneration; S for Saranac). It is purple‐flowered and phenotypically similar to Saranac. One‐gram lots of Regen‐S seed are presently available for distribution, and larger amounts are expected to be available in late 1975. A yellow‐flowered regenerator ‘Regen‐Y,’ is now being bred from selections out of ‘Rhizoma,’ ‘Rambler,’ and ‘Drylander.’ Small amounts of Regen‐Y seed are also presently available, thus providing a contrasting qualitative genetic marker stock.