In the years 2010 and 2011 experiments with manual cluster thinning had been executed on the red vine variety Zweigelt in the Weinbaugebiet Neusiedlersee-Hügelland (Burgenland, Austria). The aim of this study was to search for effects of a 0.5 cluster thinning (0.5CT) and a single cluster thinning (STC), which had been established only 2 weeks after flowering (BBCH 73), on physiological parameters, water relations and quality parameters compared to vines without cluster thinning. In both, referring to weather conditions, very different experimental years, the leaves of shoots (1st to 6th node) without crop thinning generally showed a more negative predawn water potential (PWP), a lower relative water content (RWC) and therefore more water stress, a lower N- and Mg-concentration and a less negative osmotic potential (lower concentration of osmotic active substances). Also, the berries of this unthinned control showed a lower RWC, a less negative osmotic potential (OP), a lower ascorbate content, less N, more Ca, a lower berry weight and, however an approximately similar level of must weight at harvest. Whereas under unfavorable climatic conditions (2010) distinctly more titratable acid (about 3 g/l) was present in the berry juice. In the sunny year (2011) there was hardly a difference as to that. The unthinned grapevines reacted with more intense year dependent fluctuations (yield, must weight, titratable acid) compared with cluster thinned ones. By comparison of both cluster thinning practices, leaves of the SCT had a better water supply (referring to PWP and RWC), a higher N- and Mg-content and a more negative OP. The berries of the SCT had a higher RWC, a more negative OP, a higher ascorbate content, more N and more relevant N-compounds for alcoholic fermentation, less Ca, a higher berry weight and volume and the most intense earliness in ripening.