The spatial variability of hydraulic conductivity at the site of a long-term tracer test performed in the Borden aquifer was examined in great detail by conducting permeability measurements on a series of cores taken along two cross sections. Along the two cross sections, a regular-spaced grid of hydraulic conductivity data revealed that the aquifer is comprised of numerous thin, discontinuous lenses of contrasting hydraulic conductivity. A value for the longitudinal macrodispersivity calculated from statistical parameters using three-dimensional stochastic transport theory developed by L.W. Gelhar and C.L. Axness (1983) is about 0.6 m. For the vertically averaged case, the two-dimensional theory developed by G. Dagan (1982, 1984) yields a longitudinal dispersivity equal to 0.45 m. Use of the estimated statistical parameters describing the 1n (K) variability in Dagan's transient equations closely predicted the observed longitudinal and horizontal transverse spread of the tracer with time. (Copyright (c) 1986 by the American Geophysical Union.)