Approximately 60-70% of small cell lung carcinoma (SCLC) cases are diagnosed at extensive stage, thus tumor markers for its early detection are needed. Autoantibodies associated with malignancy are present before radiographic detection. Autoantibodies detected using the autoimmune target (AIT) test in patients with some tumors have shown the possibility of autoantibodies to be used as a tumor marker. To overcome the limitations of antinuclear antibody (ANA) test using HEp-2 cell line, the AIT test was developed using human macrophage cell line, IT-1, as a substrate, which showed positive identification of various autoantibodies with a higher level of sensitivity. We report a case of SCLC with autoantibodies against proliferating cell nuclear antigen (PCNA) and centriole in a 70-yr-old man who had a history of heavy alcohol consumption and a 50 pack-yr history of smoking. Results of computed tomography of the chest and abdomen showed a lung mass and multiple metastases. Extensive stage SCLC was confirmed using sputum cytology and lymph node aspiration biopsy. Anti-PCNA (1:1,280) and anti-centriolar (1:320) patterns were detected using the AIT test. Neuron-specific enolase was elevated (38.2 ng/mL). There was no evidence of systemic autoimmune rheumatic disease or chronic hepatitis. This is the first case report in which coexisting autoantibodies against PCNA and centriole associated with SCLC were detected using the AIT test. This case provides some evidence that autoantibodies may be used as a tumor marker for SCLC.