Radon mitigation can be accomplished by source removal and exclusion by sealing, local ventilation, and dilution of the radon gas. Each of these approaches can have a direct impact on heating, ventilating, and air conditioning (HVAC) operation within the building volume. Conversely, HVAC operation can also directly affect the ability of the mitigation system to function properly, Air infiltration rates and interzone flows have been measured using perfluorocarbon tracer techniques in research houses with radon problems in west central New Jersey, These tests have been augmented in two houses with constant concentration tracer gas techniques to provide further information. Using a typical basement subslab depressurization (SSD) system employing a fan to lower the pressure in the gravel aggregate under the slab, significant flow of conditioned space air is entrained into the system from the basement. This flow, in turn, can alter the pressures and flows in other areas of the building. Since subslab depressurization depends on lowering subslab pressures at least a few pascals, HVAC operation in the building that also lowers basement pressures can interfere with mitigation strategies. These various phenomena will be discussed.