The paper presents long term probability distributions of rain attenuation exceeded in 0.5-h, 1-h, 2-h, 4-h, 8-h, 12-h and 24-h contiguous periods of the day, at 11.6 GHz, circular polarization, in satellite radio links, at two sites in Italy (Gera Lario and Fucino). These data can be useful to match the system design to the time of the day, which can be affected very differently by rain attenuation. The results can be scaled to higher frequencies and are directly applicable to actual satellite TV and radio broadcasting, and to telecommunication systems in the 12 GHz band. The data have been obtained by applying the synthetic storm technique (after testing its predictions in the 4-h case against experimental long term results) to a large and statistical reliable set of rain rate time series collected in five years (1978-1982) of continuous observation during the satellite SIRIO experiment, in slant paths of elevation angles 32/spl deg/ and 33/spl deg/. The number of concurrent rain rate (and rain attenuation) time series considered is 587 for Gera Lario and 562 for Fucino, a very large data bank.