The 49 cultivars in the Fifth International Spring Wheat Yield Nursery (ISWYN) were grown as single plants in pots and 16 characters measured. Grain yield of the cultivars as single plants was not significantly correlated with ISWYN mean grain yields, although there were high correlations between single-plant and field performance in days to ear emergence, height, and 100-grain weight. ISWYN cultivar mean yields were used as the dependent variable in a stepwise regression analysis with the 16 single-plant characters as the independent variables. Harvest index accounted for 71.7% of the variability in ISWYN yields, and days to emergence of leaf 7 and 100-grain weight raised this to 78.5 % in a multiple regression. These results suggest a new, indirect method of predicting relative mean yields of wheat genotypes.