Isolated left ventricular noncompaction (LVNC) is an increasingly-recognized cardiomyopathy, and the possibility that it exists as a spectrum of disease has yet to be explored. We sought to determine the prevalence, spectrum, and functional consequences of LVNC; 2 blinded reviewers assessed 500 transthoracic echocardiograms for LVNC for adequate study quality, absence of co-existing cardiomyopathy, and LVNC. If present, the ratio of the maximum linear length of noncompacted to compacted myocardium (NC/C) and the planimetered area of LVNC on apical 4-chamber view were measured. Patients were classified by degree of noncompaction measured by either the NC/C ratio or LVNC area as controls, mild, moderate, and severe; 380 patients were included in the analysis and 60 (15.8%) had evidence of noncompaction. Patients with increasing severity of noncompaction had significantly decreased ejection fractions. In conclusion, these findings indicate that LVNC may be more common than previously recognized and may exist as a spectrum, which can be classified using the NC/C ratio or LVNC area classification schemes.