Vernalization response genes are known to contribute indirectly to grain yield by influencing flowering time, number of tillers and spikelets in sensitive wheat genotypes. There has been no report of the effect of vernalization on grain fill duration and grain weight in wheat. The objective of this study was to investigate the effect of vernalization on grain fill duration and grain weight in a set of 5 high latitude spring wheat, differing in vernalization response, and their 10 F 1 hybrids obtained from a one-way diallel cross. The 15 genotypes were grown with and without 42d-vernalization treatment. Vernalization altered grain fill duration and grain weight in both sensitive and in-sensitive genotypes and no clear pattern was observed in terms of the vernalization responsiveness of the genotypes. No correlation was found between grain fill duration and grain weight in vernalized and non-vernalized treatment, indicating that the increase in grain fill duration of some of the genotypes with vernalization did not have an effect on grain weight. In order to harvest the full yield potential, vernalization sensitive genotypes may be grown in those eco-regions of high northern latitudes where growing season is relatively long and where temperatures are usually above the vernalization range.