The paper presents an evaluation of the specific rain attenuation for the frequency range of 5 - 100 GHz from Drop-Size Distribution (DSD) measurements made in the tropical region of Sao Paolo-Brazil, using a Joss disdrometer sampling the rain spectra during convective precipitation events. The attenuation of the eletromagnetic radiation was computed from the total attenuation cross section of a drop as derived by Atlas and Ulbrich (1974). A comparisonwith the Marshall-Palmer (MP) drop-size distribution was performed. The nature of the spectra observed in this region is quite different from the MP negative-exponential model which has been largely used in the calculation of microwave attenuation due to rain.