The Pd(NH3)(4)(2+)-loaded NaY zeolite was found to be a highly active catalyst precursor for Suzuki-Miyaura (SM) reactions of aryl bromides and aryl chlorides at low Pd concentrations in air. Aryl bromides and arylboronic acids can couple effectively both in pure water and in N,N-dimethylacetamide/water mixtures (1/1) within minutes with turnover frequencies (TOF) up to 4 x 10(5) h(-1). The presence of a minute amount of water was crucial for the success of the reaction with chloroarenes. The excess amounts of as-received zeolite provided the necessary water for the reaction. The results suggest that the combined use of the water-zeolite system may have a synergistic effect in the reaction. (c) 2007 Elsevier B.V. All rights reserved.