Twenty-five large broad-breasted white turkeys were fed a 22% protein diet supplemented with 500 ppm furazolidone from day 1 to 3.5 weeks of age and the same diet supplemented with 700 ppm furazolidone until 9.5 weeks of age. Following the development of round heart disease as indicated by altered electrocardiograms the 25 turkeys were sacrificed. In the livers of turkeys with biventricular dilatation (72% of cases) there was bile duct hyperlasia, portal fibrosis and intracytoplasmic globules in the hepatocytes. Globules stained pink with hematoxylin-eosin, deep red with PAS and variable with Massons trichrome stains in paraffin-embedded liver sections. Clear intracytoplasmic vacuoles demonstrable in hepatocytes of PAS stained liver sections embedded in paraffin did not stain as lipid in frozen sections but did contain sparse flocculent material in 1 micrometer sections of liver embedded in epoxy resin and stained with toluidine blue. At the subcellular level, the intracytoplasmic globules in hepatocytes were surrounded by a single membrane, contained flocculent material and had enzymatic properties characteristic of lysosomes. Blood pressure, heart rate, dp/dt max, total plasma proteins and plasma trypsin inhibitory capacity of turkeys with round heart disease were lower than corresponding values for control turkeys. Control turkeys did not exhibit the characteristic gross or microscopic lesions of round heart disease.