Improvement of oil and protein concentrations is a primary breeding objective for canola (Brassica napus L.) grown in the low rainfall areas across southern Australia. This study investigates the relative influences of genotype and environment on the relationship between seed oil concentration and protein concentration of meal, and between seed components. The study also estimates the magnitude of genetic and genotype x environment variances in oil and protein concentrations in a set of interstate field evaluation experiments of genotypes with early and mid-season maturity conducted across southern Australia in 1996 and 1997.The oil concentration of seed ranged from 36 to 46% across maturity groups, locations, and years. The range of protein concentration of meal was 30-46%. Environment had a much larger impact than genotype on oil concentration of seed and protein concentration of meal. Several genotypes in this study had higher concentrations of oil in the seed and protein in the meal than the commercial cultivars used as controls. Significant (P < 0.05) genetic variance (σ(2)(g)) and significant genotype x year x location interaction (sigma(gyl)(2)) was present in these 2 quality traits. However, the variance components for the interaction of genotype with location (sigma(gl)(2)) and with year (sigma(gy)(2)) were not significant (P > 0.05), indicating that ranking of genotypes remained constant across locations averaged over many years and across years averaged over many locations, respectively. A significant negative correlation (r = -0.73) between seed oil concentration and protein concentration of meal was observed across locations in 1997. Among the genotypes tested, there was no genetic correlation between these 2 traits, suggesting that seed oil concentration and protein concentration of meal can be increased simultaneously by selection. Increase in oil concentration of seed and protein concentration of meal was at the expense of seed residue.