Hydraulic properties and upscaling characteristics of low-permeability fractured rock are analyzed based on systematic well test data from three different measurement scales. First, tests are simulated in a large number of geological fracture network realizations, and the acceptable fracture transmissivity distribution parameters that produce the observed statistics of the two smallest measurement scales, i.e., 2-m and 10-m scales, are defined. Instead of a single value, a range of acceptable parameter values can be found to produce the observed result. Second, upscaling simulations are carried out with the calibrated networks. These indicate that the investigated system cannot be properly modeled by means of a continuum tensor presentation but would better be represented by means of equivalent fracture statistics. Third, the conductive characteristics of the calibrated 30-m network blocks are compared to well test results from the same scale. The results from this preliminary analysis indicate that one-dimensional borehole observations interpreted with standard continuum-based methods may considerably underestimate the three-dimensional conductive characteristics of heterogeneous, noncontinuum fractured media. ¿ 2000 American Geophysical Union