This paper introduces a new approach for a fractional dimension analysis of constant rate interference (or cross-hole) tests. The method does not require type curve matching and consists of a straight-line analysis approach. The approach assumes infinitesimal source conditions at both pumping and monitoring wells. The hydraulic head solution at the monitoring well is differentiated with respect to time and rearranged so that a linear relation between the variables is obtained. A semilog plot of the derivative group against time-1 produces a straight line; the slope and intercept of this line may be combined with data from the pumping well for a fractional dimension analysis of the monitoring well data. ¿ American Geophysical Union 1994