Although occupational epidemiological studies and animal experimentation provide strong evidence that radon-222 (²²²Rn) progeny exposure causes lung cancer, residential epidemiological studies have not confirmed this association. Past residential epidemiological studies have yielded contradictory findings. Exposure misclassification has seriously compromised the ability of these studies to detect whether an association exists between ²²²Rn exposure and lung cancer. Misclassification of ²²²Rn exposure has arisen primarily from: 1) detector measurement error; 2) failure to consider temporal and spatial ²²²Rn variations within a home; 3) missing data from previously occupied homes that currently are inaccessible; 4) failure to link ²²²Rn concentrations with subject mobility; and 5) measuring ²²²Rn gas concentration as a surrogate for ²²²Rn progeny exposure. This paper examines these methodological dosimetry problems and addresses how we are accounting for them in an ongoing, population-based, case-control study of ²²²Rn and lung cancer in Iowa