Aims: The usefulness of 3D echocardiography (3DE) for accurate evaluation of left ventricular (LV) remodelling after acute myocardial infarction (AMI), and early identification of remodelling in the subacute phase, was assessed., Methods and Results: Thirty-three AMI patients (21 anterior AMIs) underwent 3DE prospectively at baseline (6+/-4 days) and at 3, 6, and 12 months post-AMI. Remodelling was defined as >20% increase in end-diastolic volume (EDV) at 6 or 12 months in relation to baseline. In patients with remodelling (n = 13) at baseline, EDV and end-systolic volume (ESV), but not ejection fraction (EF), were significantly increased compared to patients without subsequent remodelling (n = 20). At 12 months, EDV and ESV increased further and significantly, and EF was unchanged in patients with remodelling, whilst LV volumes were unchanged and EF slightly increased in patients without remodelling. Clinical, electrocardiographic, and echocardiographic variables were analysed for the early identification of LV remodelling. Of these, at baseline the 3D sphericity index (EDV divided by the volume of a sphere, the diameter of which is the LV major end-diastolic long axis) was, by far, the most predictive variable with a sensitivity, specificity, and positive and negative predictive value for a cutoff value of >0.25 of 100%, 90%, 87% and 100%, respectively., Conclusions: Three-dimensional echocardiography can differentiate patients with and without subsequent development of LV remodelling accurately and early on the basis of the 3D sphericity index, a new and highly predictive variable.