In the TIME trial, the timing of stem cell delivery in patients with ST-segment elevation myocardial infarction (STEMI) was investigated. Patients with STEMI who were reperfused with primary percutaneous coronary intervention and stenting and had a left ventricular ejection fraction ≤45% received treatment with bone marrow mononuclear cells (n = 65) or placebo (n = 30). Irrespective of whether the cells were delivered 3 days or 7 days after the infarction, the injection of bone marrow mononuclear cells did not improve outcomes at 1 year relative to placebo treatment.