Objective To determine the prevalence, clinical correlates and the effects on outcome of vitamin B<inf>12</inf> and folic acid levels in patients with chronic heart failure (HF). Methods We studied an international pooled cohort comprising 610 patients with chronic HF. The main outcome measure was all-cause mortality. Results Mean age of the patients was 68±12 years and median serum N-terminal prohormone brain natriuretic peptide level was 1801 pg/mL (IQR 705-4335). Thirteen per cent of the patients had an LVEF >45%. Vitamin B12 deficiency (serum level <200 pg/ mL), folate deficiency (serum level <4.0 ng/mL) and iron deficiency (serum ferritin level <100 μg/L, or 100-299 μg/L with a transferrin saturation <20%) were present in 5%, 4% and 58% of the patients, respectively. No signi ficant correlation between mean corpuscular volume and vitamin B<inf>12</inf>, folic acid or ferritin levels was observed. Lower folate levels were associated with an impaired health-related quality of life ( p=0.029). During a median follow-up of 2.10 years (1.31-3.60 years), 254 subjects died. In multivariable proportional hazard models, vitamin B<inf>12</inf> and folic acid levels were not associated with prognosis. Conclusions Vitamin B<inf>12</inf> and folate deficiency are relatively rare in patients with chronic HF. Since no significant association was observed between mean corpuscular volume and neither vitamin B<inf>12</inf> nor folic acid levels, this cellular index should be used with caution in the differential diagnosis of anaemia in patients with chronic HF. In contrast to iron deficiency, vitamin B<inf>12</inf> and folic acid levels were not related to prognosis.