Cuthbert, R. D., Crow, G. and McVetty, P. B. E. 2011. Assessment of seed quality performance and heterosis for seed quality traits in hybrid high erucic acid rapeseed (HEAR). Can. J. Plant Sci. 91: 837-846. Hybrids are becoming the dominant cultivar type in Brassica napus L. to utilize the well-documented heterosis for seed yield in canola/rapeseed. While there are numerous reports of heterosis for agronomic traits in B. napus hybrids, there are few reports of heterosis for seed quality traits in this species. The objectives of this study were to determine if high parent or commercial heterosis for any seed quality traits occurs in high erucic acid rapeseed (HEAR) hybrids. Seed quality performance of 45 F₁B. napus HEAR hybrids, derived from crosses of 12 geographically and genetically distinct (based on known pedigrees) HEAR cultivars/lines, was assessed in the current study using seven HEAR cultivars/lines developed by the University of Manitoba (UM) and five proprietary European (EU) HEAR cultivars/lines. Replicated field trials to assess seed oil, protein, sum of oil and protein, glucosinolate, and erucic acid concentrations were conducted over six environments in Manitoba during 2004 and 2005. High parent heterosis and commercial heterosis for seed oil concentration up to 9% and up to 14%, respectively, was observed with hybrids displaying seed oil concentrations as high as 533 g kg^-1. Low parent heterosis for protein and glucosinolate concentrations was also observed. Erucic acid concentration displayed commercial heterosis. Many hybrids displayed near zero percent heterosis for any seed quality traits; however, overall seed quality was maintained or increased even in these hybrids. The results of this study indicate that development of HEAR hybrids can be an effective way to improve seed quality components, especially oil concentration, in this crop.