49 patients with primary affective disorders maintained on lithium were evaluated over a 6-month course and the pattern of 10 well-known innocuous side effects of lithium therapy was closely evaluated. The patients had significantly more side effects in the 1 st month as opposed to the 4th through 6th months. The difference was statistically significant (with p less than 0.05). There was no difference in plasma lithium levels among individuals having no side effects, 1–2 side effects or 3 or more side effects at any point during the 6-month period.