Twelve commercial sunflower hybrids were evaluated as possible standards for classifying sunflower hybrids into maturity groups at the different growth stages of sunflower for maturity classification of new hybrids in the U.S. Due to the narrow range among hybrids only four maturity classes were determined. Hybrids earlier than NK 231 were classified as the earliest group, between NK 231 and D-3868 as the second maturity group, between D-3868 and C-187 as the third group and hybrids later than C-187 as the latest maturity group. This grouping system was based on mean separation procedures using LSD values, and lowest MSEs. For detailed evaluation of physiological maturity, H-311 and K-8806 could be used as additional standards of very early and very late hybrids to give six maturity groups.