HAPLOIDS are valuable for new approaches to genetic, cytogenetic and breeding research in plants such as cultivated alfalfa, Medicago sativa L., which behave as auto-tetraploids. Their use is limited in this species, however, by the lack of a technique for their isolation; only three haploids have been reported1–3. Recently, we isolated eight haploids (2n = 2x = 16) from cultivated alfalfa (2n = 4x = 32) among the progeny of 4x−2x crosses, designed to facilitate the detection of haploids. Thus 4x−2x crosses provide a simple and effective method of obtaining alfalfa haploids.