The comparison of sleep EEG between 2 species of macaca (Macaca radiata and Macaca mulatto) shows some important differences. The light sleep (stages 1 and 2) is more important in Macaca radiata, the deep sleep (stages 3 and 4) more important in Macaca mulatta. Such differences show that the sleep pattern is not a genus particularity. In fact the species of one genus can have different sleep patterns. A study of these differences factors is attempted.