The effects of vertical faults on steady state groundwater flow are simulated using simple analytical solutions for horizontal flow across three domains that are linked by requiring continuity of head and flux. Hydraulic properties are vertically averaged, so that changes in transmissivity can be used to account for changes in aquifer thickness, juxtaposition of different aquifers across the fault, or some combination of the two. Vertical flow along the fault can be included through the use of a source-sink term. Different combinations of transmissivity contrast and recharge/discharge produce distinct head profiles, which can be used to qualitatively infer the nature of real hydrogeologic systems. Observed hydraulic gradient ratios can also be used to calculate transmissivity ratios, and if information about fault zone thickness and an independent estimate for one of the three transmissivities is known, the magnitudes of the remaining two transmissivities can be calculated. Use of the model to interpret real flow systems is demonstrated using an example from the Albuquerque Basin, New Mexico. ¿ American Geophysical Union 1995