Ab initio calculations have been performed to obtain the polarizability of water clusters (H2O)(n) up to n=20. It is shown that a simple linear relation involving the aggregation number fits the polarizability results extremely well (with correlation coefficient >0.999) indicating a near additive nature of this quantity for weakly bonded molecular clusters. Calculated dynamic polarizabilities are also shown to follow the same trend. The effect of electron correlation on the static polarizability of water clusters has also been investigated. <(C)> 2003 American Institute of Physics.