Wheat ( Triticum aestivum L.) grain Zn data from six open-top chamber experiments performed in south-west Sweden were combined to study the relationship between Zn accumulation and grain yield, grain protein, and yield components. Treatments included, in addition to open-top chamber controls, elevated CO 2, elevated O 3, combined CO 2 and O 3 exposure, combined elevated CO 2 and supplemental irrigation, supplemental irrigation, and ambient air comparison plots. The grain Zn concentration was strongly correlated with grain protein ( R 2 = 0.90) over the range of the experimental treatments, representing non-soil factors. A significant yield dilution effect was found for Zn. For a 10% increase in grain yield, Zn yield was increased by 6.8% on average. Effects on Zn yield correlated strongly with effects on grain protein yield, with a slope close to unity, showing that yield dilution effects for grain Zn and grain protein were similar. Treatment effects on grain Zn concentration were related to effects on grain weight ( P < 0.01) and grain number ( P < 0.05), but not to harvest index. It was concluded that yield stimulation caused by rising CO 2 concentrations is likely to lead to reduced Zn concentrations of wheat grain, thus reducing the nutritional quality.