Well storage effect is generally considered while interpreting pumping test data from large diameter wells. However, in an aquifer of low permeability, the well storage is found to be significant during pumping tests conducted on bore wells. The interpretation of such data gives ambiguous results unless well storage effect is taken into account. A field example is presented to illustrate the difficulty in interpretation of the pumping test data. In order to take into account the well storage effect, a finite difference approach of interpreting pumping test data is suggested.