The distribution of radon daughters and concentration of aerosol fission products in the troposphere was measured over the USSR during several periods from 1963 to 1968. An intensive fission product transport from the stratosphere to the troposphere occurs on the cyclonic side of the jet stream. As a rule, the inclusion of these products in the surface air is observed on the anticyclonic side of the jet stream. The simplest theoretical scheme is given to describe the vertical distribution of radon and fission product concentrations in the troposphere; the theory takes into account the vertical turbulent exchange coefficient and vertical motion. The directions of vertical motion, estimated from the vertical distribution of both radon and fission products in the troposphere, agree very closely with meteorological data.