Lymphoid hamartomas are a rare benign disease which can be easily treated by complete surgical excision. They developed most often in the thorax, and can be discovered usually on routine chest X-ray.p But some of them can also be found because of pressure symptoms or the presence of a palpable mass if outside the thorax. We experienced a case of the hyaline-vascular type of lymphoid hamartoma in the left hilum of a 29 year-old Korean male in March, 1979. He was well except intermittent cough and left chest discomfort of a year duration and was treated by resection of the left upper lobe including nodular tumor masses. The histological characteristics were an aggregation of lymphoid follicles composed of concentrically arranged mature lymphocytes with centrally placed thick walled arterioles showing endothelial proliferation and some of them were hyalinized. Between the follicles, there was extensive capillary proliferation and infiltration of numerous lymphocytes, scanty plasma cells and eosinophils.[KTCS 1979;2:101-104]