The relationship between the decay products of Rn(DRn) and ThB concentrations in the atmospheric air and the stability of the atmosphere has been established. Daily measurements were taken over nearly a 2-year period (1989--1991). The method used to determine concentrations of DRn and ThB is based on the total alpha activity amount of radioactive aerosols deposited on a filter. The vertical stability of the atmosphere was studied by three methods: Pasquill's stability categories, vertical temperature gradients, and a method based on Montgomery's potential. In the last two cases the relationship between the concentrations in DRn and ThB with stability was higher and more concordant with experimental results than with Pasquill's method. ¿ American Geophysical Union 1992