A stochastic approach is adopted for characterizing the uncertainty in well capture zones in heterogeneous formations. Transmissivity is modeled as a random space function and a Monte Carlo approach is used to infer the probability distribution of the resulting stochastic capture zones. Through several numerical experiments, the influence of the statistical parameters of transmissivity variation on the extent of uncertainty in the location of the capture zone is investigated. Two aquifer models are considered: a fully confined aquifer and a leaky-confined aquifer receiving recharge from above. A connection is made with previous work on transport theory, and the statistical parameters of the capture zone probability distribution are compared with those of a solute concentration plume. ¿ 1998 American Geophysical Union