A residence in Roxboro, NC, was found to have its well-water supply contaminated with benzene (approx 300 microgram/l) and other organic compounds. The residents of the house do not currently drink the water, but they use it for daily showers. A study was designed to monitor and model short-term benzene dispersion within the house during and after a shower. A multizonal mass balance model, CONTAM88, was used to predict interzonal air flow rates and benzene concentration distributions within the house. The idealization of the building was created using NBSAVIS, a preprocessor to CONTAM88. Simulation results showed that the highest concentration occurred in the shower stall. Benzene concentrations in the master bedroom and other rooms were lower. Simulated benzene concentration distributions showed that benzene from the shower rapidly dispersed in the house, and reached equilibrium in all the rooms in less than 30 minutes after the shower. These results were supported by SF6 experimental data. Benzene samples were collected using glass, gas-tight syringes in the shower stall and at various locations in the house. The average benzene concentration after a 20-minute shower was 978 microgram/cu m in the shower stall, 263 microgram/cu m in the master bathroom, and 70 microgram/cu m in the master bedroom. Simulated and average measured benzene concentrations yielded a similar behavioral trend. It was concluded that multizonal mass balance models may be useful in designing field study monitoring strategies.