In the light of the existence of controversial reports on the stability of Li ratio, we investigated a group of affective patients wishing to verify intraindividual stability of this parameter in the different phases of the disease, that is normothymia and manic and depressive episodes. We found lower Li ratios for the periods preceding any relapse. Further, we analyzed whether or not some epidemiological factors, such as polarity, sex, actual age, age of onset, might affect interindividual variability of the Li ratio. We found that they did not as single factors. Interaction between polarity and the presence of relapses appeared to significantly affect the Li ratio.