Fruit from 2 trees of each of 17 sour cherry cultivars were harvested in 1983 and 1984 and evaluated for 6 traits: fruit diameter and length, fruit firmness, soluble solids, and pit length and width. The amount and relative importance of the genetic and environmental variability were determined and used to develop a sampling scheme required for a specific level of genetic discrimination. Genetic differences accounted for the major component of the variability for fruit diameter and length and pit length and width. Soluble solids was the only trait with a significant year variation and year × cultivar interaction. In general, 5 fruit per tree and 2 trees per cultivar would detect the desired differences for fruit diameter and length and pit length and width, while a larger number of replications would be necessary to detect genetic differences for fruit firmness and soluble solids.