A case of oat-cell carcinoma arising in the pericardium of a 51-year-old woman is described. The patient had multiple nodes; the largest was 2 x 1 cm. Two years later the patient presented with a tumor on her lower gum; this measured 2 mm and had similar characteristics to the previous one. The immunohistochemical study showed strong positivity for neuron-specific enolase. From review of the literature, it may be concluded that this is the first report of oat-cell carcinoma occurring in the pericardium.