Afyonkarahisar and its surroundings are in the middle of the Akşehir-Simav Fault System. Before the earthquakes in the region, radon anomalies were observed in some well waters. Linear equations between radon minima and earthquake magnitudes (Mw) were obtained, and correlation coefficients (R2) were calculated. The correlation coefficient (R2) values of the wells from 1 to 6 were obtained as 0.93, 0.83, 0.82, 0.97, 0.87 and 0.85, respectively. Good correlations (high R2 values) were obtained between the radon minimum and the earthquake magnitude (Mw) in 6 wells. The precursory minimum observed at the radon concentration in groundwater decreased as the earthquake's magnitude increased.