Implantation of malignant cells along the needle aspiration tract is an extremely rare potential complication following a percutaneous fine needle aspiration biopsy of a lung carcinoma. The dissemination of malignant cells by a needle aspiration biopsy may convert an operable and potentially curable lesion into a fatal disease. We report two cases of chest wall implantation of carcinoma of the lung after a thin needle aspiration biopsy. A fifty-five year old male was successfully treated by a radical full-thickness excision of the chest wall and immediate reconstruction with the latissimus dorsi musculocutaneous island flap. A sixty-eight year old female was treated with a partial-thickness excision of the chest wall and skin graft due to superimposed infection and ulceration of the metastatic chest wall carcinoma. One case lived for 31 months up to November 1994, and the other's condtion has been uneventful for 3 months up to now.