Cultivars of wheat, barley, oats and rye were grown at 12 locations throughout Manitoba over 2 consecutive years. The concentrations of macrominerals Ca, P, Mg, K and S, and of microminerals Cu, Zn, Mn and Fe in the grains were determined and found to differ (P < 0.05) among cultivars of each grain. These differences among cultivars were considered to be minor, however, when comparisons between mineral concentrations and dietary requirements of economically important livestock were made. Location and year of growth (environmental variance) were factors affecting the concentrations of Cu, Zn and Mn, accounting for 72–96% of the total variance in these mineral concentrations (total variance = environmental variance plus cultivar × environmental variance). The concentrations of macrominerals in cultivars of wheat or barley differed among locations and year of growth, with cultivar × environment effects accounting for 25–50% of the total variance observed, except for S where these effects accounted for 86–87% of the total variance; this percentage was lower for oats and rye where a lower number of cultivars or locations was evaluated. Variation in mineral concentrations in the four Manitoba-grown grains was often considerable with coefficients of variation ranging from 8.5 to 40.1%. With all cereal grains, supplemental Ca, P, K, S, Cu, Zn, and Mn would be required to insure adequate dietary intakes for ruminants in general and Mg for lactating dairy cows, with Ca, P, Zn and Fe required for swine and poultry, Mn required for poultry and K required for some classes of poultry. Supplemental Cu would be required with wheat-based diets fed to swine and poultry. Key words: Minerals, wheat, barley, oats, rye, Manitoba