The effects of age and size of seed on seedling vigor, rate of respiration, and 2,3,5‐triphenyl‐2 H ‐tetrazolium chloride (TTC) reduction by germinating seeds were studied in the laboratory. Wheat seed ( Triticum aestivum ssp. compactum (Host) MacKey ‘Elmar’) was used. Stratification was necessary to eliminate the effect of dormancy in the youngest seed class. Significant positive correlations were found between rate of emergence and vigor (ability to emerge from deep seeding), emergence and rate of respiration, and between vigor and both tetrazolium reduction and rate of respiration for seed of different ages. With different seed size classes, significant positive correlations were found between seed weight and tetrazolium reduction, and between shoot weight per plot and tetrazolium reduction. In a preliminary test, varietal differences in seedling vigor, which were largely due to relative coleoptile elongation, were not correlated with TTC reduction. The possible place of TTC reduction as an empirical seedling vigor test and respiration of germinating seeds as a component of vigor are discussed.