The recurrence rates during lithium preventive treatment were investigated in a sample of 270 Mood Disorder subjects subdivided according to their onset time for lithium prophylaxis as very early (within 5 years from the onset of illness), early (6-10 years), late (11-20 years) and very late (more than 21 years). 131 subjects of the sample followed for 4 years prolonged the observation for a further period of 8 years. Results indicated that beginning lithium therapy within the first ten years of illness predicts better preventive outcomes than beginning prophylaxis later, both in major depression, recurrent and bipolar patients.