Environmental measurements of Radon and its progeny were carried out in a gold mining area in the department of Antioquia, Colombia. Radon concentration measurements were carried out during 2 y in seven different measurement points in three types of geological zones, by using EPERM electret chambers and DOSEman Pro detectors at each point. Radon concentration values between 858 ± 59 Bq m-3 and 2469 ± 158 Bq m-3 and an equilibrium factor between 0.15 and 0.27 were found. The annual effective dose, taking into account the radon concentration, was determined under two calculation methodologies ([1] and International Commission of Radiological Protection 137), obtaining values of up to 7.7 mSv, and 13.5 mSv, respectively, for 2000 annual working hours, which shows the importance of the dosimetric data and epidemiological studies carried out year after year to reduce the uncertainties regarding estimates of radon exposure and the need to carry out individual monitoring of miners.