The present study investigated the safety, feasibility, and potential efficacy of autologous bone marrow cell injection in patients with chronic myocardial infarction and severe left ventricular (LV) dysfunction. In 15 patients (63 ± 9 years; 14 men) bone marrow was aspirated from the iliac crest. Using the NOGA system (Biosense-Webster, Waterloo, Belgium), 94 ± 14 × 10⁶ bone marrow–derived mononuclear cells were injected into the infarction border zone. Bone marrow cell injection was performed without periprocedural complications in all patients. At 2.5 months, 1 patient died from worsening heart failure. New York Heart Association class improved from 3.5 ± 0.5 at baseline to 2.7 ± 0.8 at 3 months (p <0.01) and 2.9 ± 0.8 at 6 months (p <0.01 vs baseline). LV ejection fraction (technetium-99m tetrofosmin single-photon emission computed tomography) increased from 23 ± 8% to 27 ± 9% at 3 months (p = 0.02) and regional wall thickening improved from 12.8 ± 5.9% to 15.3 ± 7.2% at 3 months (p = 0.02). Injected myocardial segments displayed a significant improvement in regional wall thickening (6.6 ± 6.3% vs 11.7 ± 7.0% at 3 months, p <0.01) and perfusion score (3.5 ± 0.7 vs 3.0 ± 0.9 at 3 months, p = 0.02) and a trend toward an improved fluorine-18 fluorodeoxyglucose score (2.9 ± 0.9 vs 2.6 ± 1.0 at 3 months, p = 0.06). Regional wall thickening (16.5 ± 8.9% vs 19.1 ± 9.1% at 3 months, p = NS), perfusion score (1.8 ± 0.4 vs 1.7 ± 0.5 at 3 months, p = NS), and fluorodeoxyglucose score (1.7 ± 0.4 vs 1.6 ± 0.4 at 3 months, p = NS) did not improve in noninjected myocardial segments. In conclusion, bone marrow cell injection in patients with chronic myocardial infarction and severe LV dysfunction is safe and feasible and appears to be associated with a decrease in heart failure symptoms and an improved LV function.