Information was obtained on the reaction of segregating populations of oats (Avena byzantina C. Koch and Avena sativa L.) to soil‐borne oat mosaic virus, Marmor terrestre var. typicum. Bulk F3 lines were evaluated at two locations that had natural mosaic infestation in the soil. Frequency distributions of mosaic scores indicated that tolerance to OMV was a quantitative character. Heritability estimates based on progeny means ranging from .59 to .88 indicated that a large portion of the variability in tolerance to the virus is heritable. A heritability estimate based on individual plots was lower. Estimates of expected genetic advance indicated that selection of 5% of the more tolerant lines would result in lower mosaic scores, although the resulting scores would not approach the tolerant parent. Evaluation for tolerance at one location was a reliable indication of tolerance at the second location.