Abstract: In field trials, effects of the growth regulators Gibb 3 and Regalis® on cluster structureof grapes and the reduction of botrytis disease and sour rot disease were evaluated. Gibb 3 canonly be used on Pinot-varieties. Regalis® also can be used on Rhine-Riesling. The growthregulators Gibb 3 and Regalis® were very effective in loosening the cluster structure at Pinotvarieties.Reduction of botrytis disease was compared to fungicide treatments. In most cases, theyield of grapes decreased without an increase of the sugar content. Results of Regalis® on Rhine-Riesling varied greatly without relevant reasons. No differences were found when Regalis® wasapplied with different amount of water and at different development stages. Gibb3 proved to havea better effect if applied with greater amounts of water. The quality of red wines increasesbecause of higher anthocyan- and phenol-contents. White wines produced from grapes treatedwith Regalis® didn’t show better tasting results in spite of lower yield.