Depressed geriatric patients have lower levels of folate (FOL) than controls. Also, FOL supplement can reduce depressive morbidity. One hypothesis consistent with this is that FOL deficiency causes a lowering of CNS serotonin that contributes to depression. The present report is from one site of a multicenter study that compared an SSRI (sertraline) with a nonspecific tricyclic antidepressant (nortriptyline) in geriatric depressed patients. We added measures of FOL at baseline and outcome for 22 depressed patients older than 60 years. Both treatments were effective. At baseline, FOL levels were within the normal range. Higher FOL levels at baseline predicted greater improvement. Further study of FOL interaction with SSRI is warranted. For the group treated with the SSRI, baseline FOL level was a more efficient predictor of improvement, especially for results on a self-rating depression scale (POMS).