The New York State Department of Health has estimated and mapped radon concentrations for every town and city in the State. Since for many towns there are few indoor radon measurements, the radon estimates for these towns were determined using correlations to surficial geology. A project was conducted to target towns for additional measurements that currently have few data but, based on the surficial geology of the town, are estimated to have elevated levels of indoor radon. The objective of the project was to obtain at least 30 additional measurements for the targeted towns and to compare the measurement results with the estimates based on geology. The study completed 1606 radon measurements from 9080 detector applications mailed to home owners in 94 underserved towns spread throughout the State. Of the 1115 basement measurements, 43% 148 Bq m(-3), with a maximum of 6900 Bq m(-3). Three homes measured in one town had radon concentrations above 2900 Bq m(-3). Of the 491 living-area measurements, 19% exceeded 148 Bq m(-3), with a maximum of 2700 Bq m(-3). About 60% and 86% of measurement results were within one standard deviation and a factor of two, respectively, of estimated concentrations. Results indicate that regardless of the magnitude of radon potential, the estimates are in good agreement with measured concentrations.