Heart failure is the most common cause of hospitalization in the United States. Just as the prevalence of heart failure has increased, the number of diseases identified that result in the heart failure syndrome has escalated. Certain cardiomyopathies that have previously been regarded as very rare are being recognized with increasing frequency, because of improved imaging techniques and an increased understanding of the pathophysiologic mechanisms that result in these diseases. Improved echocardiographic techniques and methods such as spectral Doppler and 3D image rendering, along with the use of advanced diagnostic tools such as cardiac CT angiography and cardiac magnetic resonance imaging are now common. These advanced imaging methods have led to an increased appreciation of the frequency of diseases such as isolated left ventricular noncompaction and cardiac amyloidosis. Left ventricular noncompaction, once thought to occur in roughly one in one million patients, may actually be seen in fewer than one in 1000 patients. Cardiac amyloidosis, in the senile form, may exist in 80% of 80-year-old patients, although the incidence of clinical symptoms is less. As the genetic alterations that contribute to these diseases are further elucidated, improved diagnosis and a better understanding of the prognosis of these uncommon cardiomyopathies will follow.