Abstract Inheritance of traits believed to indicate cold tolerance was studied in parent and selected populations of a Nebraska derivative of the Iowa Stiff Stalk Synthetic. A nested mating design was used in both populations, and progenies were evaluated in a growth chamber experiment. A differential temperature regime of 11.1°C for 14 h with light and 5.6°C for 10 h without light was used. The study indicated that both additive and dominance variance effects were involved in the traits studied. Non-additive genetic effects appeared to be operative in the parent population. Both additive genetic effects and dominance effects were operative in the selected population. In the selected population dominance effects were most apparent for seedling vigor. Changes in additive genetic effects might reflect accumulation of favorable cold tolerance alleles through selection. Maternal influences could not be ignored in interpretation of results. Selection to improve cold tolerance using growth chamber methods resulted in more desirable, but not significantly different levels of cold tolerance.