The patient was a 39-year-old woman admitted with complaints of fever, clubbed fingers and arthralgia. A chest roentgenogram and chest computed tomographic scan revealed a mass in the left lower lobe. Transbronchial lung biopsy was performed, and a diagnosis of moderately differentiated adenocarcinoma was made. Physical examination confirmed finger clubbing in both hands. Bone scintigram showed marked accumulation of 99mTc-MDP in the long bones, bones of the elbows, and patellae. These findings yielded a diagnosis of pulmonary hypertrophic osteoarthropathy associated with primary lung cancer in young adult. The patient had fever and disturbance of gait of arthralgia on admission, and was treated with an oral non-steroidal anti-inflammation drug (NSAID). Advanced non small cell lung cancer (clinical stage T2 N3 M1, Stage IV) was then diagnosed. Gefitinib was administered after EGFR mutation was found in the tumor specimen. NSAID therapy alleviated the fever and arthralgia. After starting gefitinib and discontinuing the NSAID, She had kept a remission of rational symptom with cytoreductive effect. The abnormal findings of bone scintigrams subsequently disappeared and the patient's serum ICTP dropped.