The capability of Stratosphere-Troposphere radars for estimating the energy dissipation rate &egr; and eddy diffusivity Kz is still strongly questioned because the methods proposed in the literature generally make use of assumptions not yet fully justified. In order to clarify this point, two assessment campaigns, using the high-resolution UHF PROUST radar, have been performed. Results obtained with both width and power methods are systematically compared with a statistical approach proposed by Dewan <1979> and Woodman and Rastogi <1984>, using the thickness and lifetime of the turbulent layers. The &egr; and Kz derived from these three methods in observed turbulent fields near the tropopause level are found to be reasonably similar for turbulent layers whose thickness LT is smaller than 300 m. For the thicker turbulent patches (LT>300 m), the statistical approach using turbulent thickness tends to give eddy diffusivity values greater than those obtained with width and power methods. This discrepancy could be due to the nonhomogeneity of the turbulence in these large turbulent structures.¿ 1997 American Geophysical Union