In the paper results of trials with sunflower hybrids organized in sunflwer growing areas by the Research Institute for Plant Production Praha-Ruzyne in the vears 1984-1989 are summarized.In small--scalc trials 92 hybrids from 12 countries were tested, in mid-scale trials 59 hybrics from 5 countries. In small-scale trials vield differences between the years (always of a two-vear experimental cycle), between localities (when the assortment in the ČSFR and Austria was identical) and between hybrids themselves were compared. Hybrids were compared within the framework of each two-year cycle and in trans- formed yields also for the whole six-year period. In mid-scale trials yield analysis of the hybrids in the course of six years at three localities (at a various number of years at a locality) has been performed. As result, hybrids were assorted into yielding categories. Comparison of the success of single countries and firms according to the ranking in small scale trials prefers I ungary and GKI Szeged, in mid-scale trials the USA (firms Pionier and Northrup King), rumania and Yugoslavia were the most successfull ones.