A study was conducted to evaluate response of alfalfa (Medicago sativa L.) to selection for resistance to the root-lesion nematode (Pratylenchus penetrans (Cobb) Filipjev and Sch.-Stek.) under growth-room facilities. Six hundred plants of the cultivar Vernal were inoculated with root-lesion nematodes. Counts were made 13–14 wk later of the number of nematodes g−1 root. Selections were made for relatively low counts (resistant) and high counts (susceptible). Selections were self-pollinated, and the S1 progeny of nine plants (five resistant and four susceptible) were evaluated. The S1 progenies from both types of selections had similar counts. The S2 progenies of resistant S1 parents, however, had lower counts than those of susceptible parents. The F1 crosses generally reacted as expected on the basis of the S2 parents. Results of this study suggest that progress can be made in breeding for resistance to the root-lesion nematode in alfalfa.Key words: Nematode, Pratylenchus penetrans, alfalfa, selection