Nonpumping monitoring wells are commonly installed and sampled to delineate the extent of a contaminant plume and its chemical character. Samples from municipal and private pumping wells are frequently collected during ground-water contamination investigations as well. Pumping wells are also employed for remedial actions. To properly interpret sampling data from monitoring and pumping wells and to estimate their potential effectiveness in remedial actions, it is important to clearly define the geometry of that portion of the aquifer contributing water to the well (the capture zone). Velocity distribution plots by manual and computerized methods are illustrated and shown to be simple and of reasonable accuracy.