We have studied the possibility of using the nonequilibrium of radon daughters as an atmospheric tracer. Over a 7-month period, two daily measurements were taken, one in the early morning and another in the early afternoon at a sampling point with a continental climate. The Rn in the atmospheric air is determined by electroprecipitation of Ra A (218Po) ions, and the Ra B (214Pb) and Ra C (214Bi) daughter concentrations are evaluated by gamma spectrometry. The results show a great variation of the activity ratios Ra B/Rn and Ra C/Rn during the sampling period, depending on the time of measurements and weather conditions. The relations between the activity ratios Ra B/Rn and Ra B/Rn with the stability of the atmosphere has been studied. The stability of the atmosphere was established by two methods: Pasquill's and Turner's stability categories. In the second case, the relationship between the activity ratios Ra B/Rn and Ra C/Rn with stability was higher. ¿ American Geophysical Union 1994