Variations in radon concentrations near the earth's surface can provide important information about seismic activities. Continuous monitoring of radon concentrations is one of the important steps in predicting earthquake mechanisms. This study monitored the radon concentration of an active tectonic zone in western Turkey. Four sampling stations in the seismic area, of the Tuzla fault line, were selected for radon monitoring. The online radon monitoring system was placed at Cumali station. Concurrently, the radon concentrations in the soil gas were continuously measured using LR-115 nuclear track detectors and an online radon measurement system. Data obtained from Bogazici University Kandilli Observatory and Earthquake research Institute was incorporated in the analysis to correlate with the collected radon concentration. The radon concentrations were measured using solid-state nuclear track films (LR-115) in the soils of thermal water fields, which varied from 40 track cm(-2) week(-1) to 1580 track cm(-2) week(-1). Comparison of the radon concentration found using the above described techniques reveals that there is a linear correlation between the radon emission rate and the seismic activities in the area under investigation.