Results of a greenhouse test with eight cultivars and two selections of birdsfoot trefoil, Lotus corniculatus L., indicated that forage yields were significantly reduced by Pratylenchus penetrans (Cobb 1917) Filip. and Stek. 1941. Forage yields of all cultivars and selections at the fifth and sixth cuttings and total yields for the 285-day experimental period were significantly lower than non-infested checks. Root production was significantly reduced by P. penetrans. Reductions in forage yield and root production as a result of nematode infestation were similar for all cultivars and selections. Nematode increase by the end of the experimental period did not differ significantly among cultivars or selections. In a field test, forage yields, numbers of nematodes recovered from rootlets, and recovery of Fusarium spp. fungi from rootlets and tap roots did not differ significantly among seven cultivars.