Airborne concentration levels of222Rn and its progeny, and220Rn progeny were measured in an underground U mine. In addition, concurrent measurements of several meteorological variables such as temperature, relative humidity, barometric pressure and airflow rate were also carried out. Mining operations and mining activities during the measurements were carefully noted. The data collected show great variability. Although not particularly strong, some definite correlations could be found between airborne radioactivity concentration levels, meteorological variables, and mining operations (and mining activities). The difficulty in obtaining stronger correlations between the above variables is attributed to the great and simultaneous variability of most of the variables measured. The data presented here are typical of active U–Th mining environments, i.e., of Ontario (Canada) underground U mines. Measurements extended for a period of a full calendar year and involved several thousand independent measurements.