A 34-year-old female presented with dry cough for 2 months. Chest X-ray showed bilateral interstitial pneumonitis. Her blood anti-nuclear antibody (ANA) titer was 1: 1280. The lung lesions did not respond to ceftazidime or steroids. A subsequent lung biopsy revealed lung adenocarcionoma. In patients with high ANA titer but without specific antibodies to DNA or extractable nuclear antigens, the possibility of underlying neoplastic diseases has to be considered.