Cardiac nonamyloidotic immunoglobulin (Ig) deposition disease (CIDD) is a rare disorder characterized by Ig deposition in the myocardium associated with plasma cell dyscrasias. A retrospective review of cardiac biopsies performed at two different institutions identified eight patients with CIDD. All patients had plasma cell dyscrasias with monoclonal gammopathy. Three had IgG lambda, two had IgG kappa, one had IgD kappa and one each had free kappa and free lambda light chain. Four patients had concurrent amyloidosis involving other organs. One had amyloidosis of kidney alone, one had amyloidosis of kidney and abdominal fat pad and two others had amyloidosis of bone marrow vasculature. Three patients had dialysis-dependent renal insufficiency. None of the patients had symptoms of heart failure. Six patients had echocardiographically demonstrable concentric left ventricular hypertrophy with diastolic dysfunction. Two patients had significant cardiac arrhythmias requiring medical intervention. On endomyocardial biopsy, all eight had normal appearing myocardium on light microscopy with negative Congo Red and Thioflavin T stains. On immunofluorescent staining of the cardiac biopsies, all eight stained positive for interstitial Ig deposition. Electron microscopy (EM) confirmed the presence of granular deposits of Igs in the myocardium in five of the eight patients. EM studies were not available in one patient and two others had normal EM studies. In conclusion, CIDD should be considered in the spectrum of cardiovascular pathology in patients with plasma cell dyscrasias. They often, but not always, have left ventricular hypertrophy. These patients may be at risk for developing arrhythmias as well as diastolic dysfunction. Unless immunofluorescent and EM studies are performed routinely in biopsy material, this entity may be missed in the absence of amyloidosis. Concurrent amyloidosis in other organs sheds a unique perspective into the role of local microenvironment in the pathogenesis of systemic Ig deposition disease and amyloidosis.