ABSTRACT Objetive To identify potential clinical and epidemiological predictors of long-term response to lithium treatment. Methods A total of 40 adult outpatients followed in an university hospital, with confirmed diagnosis of bipolar disorder and with history of lithium use for at least a six months period, had their response to this medication assessed through the use of a standardized instrument. The ALDA scale is based on retrospective clinical data, in our study assessed through a thoroughly reviewed of the medical charts, and is used to evaluate the clinical improvement with the treatment (Criterion A), corrected by the acknowledgement of possible confounding factors, such as duration of the treatment, compliance and concomitant use of additional medications (Criterion B), in order to estimate the response that can be specifically attributable to lithium. Results Our study found an inverse relation between the number of mood episodes with psychotic symptoms and lithium treatment outcome. Conclusion The results reinforce the hypothesis that lithium seems to be less efficacious in patients with bipolar disorder who present psychotic symptoms.