Background Anemia is an adverse prognostic marker in heart failure (HF), but its cause and relationships with other comorbidities are uncertain. Methods All index emergency HF admissions to one urban hospital during the year 2000 were studied. Results Of 528 consecutive admissions with HF, 45% of patients (51% men and 38% women) had anemia (Hb < 13 g/dL in men and < 11.5 in women), which was usually normocytic. Anemia was equally common in patients with reduced and preserved systolic function. Hematinic deficiencies were rare, but 162 (70%) of anemic patients were lymphopenic. Median (interquartile range) C-reactive protein was higher in anemic patients compared with nonanemic patients (21 [5-211] mg/L vs T3 [5-155] mg/L, P =.0086). Marked reductions in glomerular filtration rate (< 30 mL/min per 1.73 m(2)) were more common in anemic patients (24%) than nonanemic patients (9%) (P <.0001). Median follow-up was 814 days (range 682-978 days). One hundred twenty-five (54%) anemic patients died, compared with 93 (32%) nonanemic patients (P <.00001), and anemia was a predictor of death (in patients with reduced or preserved systolic function) and death or hospital readmission. Conclusions Renal dysfunction is one probable cause of anemia in HF: The overlap of anemia and lymphopenia suggest that hematopoiesis may be more generally depressed. Anemia is a predictor of adverse outcome in HF, irrespective of systolic function.