This study was carried out during the seasons of 2000 and 2001 to evaluate the effect of potassium fertilization, each alone or with summer pruning on vine growth, yield, berry quality and changes in N, P, K, Ca and Mg in leaf petioles of Thompson Seedless grape.                 The data revealed that, potassium fertilization at 150 g/vine each alone or with summer pruning significantly increased leaf area, yield per vine, cluster and berry weight than adding potassium at 100 or 50 g/vine. Also, this treatment presented a somewhat increment in SSC/acid ratio in berry juice and NPK, but reduced the values of both Ca and Mg in leaf petioles.