Evidence for the impact of micronutrient supplementation trials on depression in women from developing countries is limited. This study examines this association and compares the impact of weekly versus daily combinations of micronutrient supplements on symptoms of depression. A randomized, positive-controlled trial was conducted in Guatemala. A total of 459 women were assigned randomly to 4 groups to receive weekly (5,000 or 2,800 microg) or daily (400 or 200 microg) folic acid (FA) plus iron, zinc and vitamin B-12 for 12 weeks. Depression was measured using the Center for Epidemiologic Studies-Depression 20-item Scale (CES-D). A score = 16 was used as an indication of depression. The association between micronutrient status and depression was assessed using baseline data. Generalized linear regression models were used to assess treatment effects. The baseline mean CES-D score was 17.1 +/- 8.5 and the prevalence of depression was 49.3%. Women in the lowest tertile of red blood cell folate (RBC) were 1.7 times more likely to be depressed than those in the highest tertile (OR=1.71; 95% CI: 0.91, 3.18). There were no associations between depression and serum folate, homocysteine, vitamin B-12, hemoglobin, ferritin or zinc (p > 0.05). Mean depression scores decreased by 2.3 points post-intervention and depression decreased to 37.7%, with no differences in degree of improvement by group (p = 0.64). Low RBC folate was associated with elevated symptoms of depression at baseline. Supplementation with FA-containing micronutrients may be equally efficacious in improving symptoms of depression when provided daily or weekly. Our findings that poor folate status may increase depression needs to be further investigated.