Synopsis Average survivals in lines of crosses among winterhardy, intermediate‐hardy, and spring oat varieties suggest that cold resistance was governed by genes having cumulative effect without important genie interactions. Some crosses showed promise as a source of combinations with more hardiness than the very winter‐hardy variety Wintok.

Synopsis A greenhouse and cold room technique is described which rates cold resistance of oat varieties in the same relative order as that in uniform hardiness experiments in the field. Of various factors influencing survival of seedlings, soil moisture content, temperature, length of cold treatment, and age of seedling had the greatest effect. Hardening treatment, thawing treatment and level of nutrition had small effects.