There are few reported cases of intrathoracic Ewing's sarcoma, a very rare malignant neoplasm. We report a surgical case of extraskeletal Ewing's sarcoma that had been followed-up as a stable sized tumour for many years, which then grew rapidly within a year. A 27-year old female patient with a rapidly growing abnormal shadow on chest roentgenogram was admitted to our department. She had undergone periodic examinations including chest computed tomography (CT) scans for 6 years since a small nodule in her chest had been pointed out by chest roentgenogram. The initial CT demonstrated a solitary nodule with a diameter of 20 mm on the parietal pleura that covered the V rib of the posterior chest wall. For 5 years the tumour's size did not change noticeably but it suddenly grew to about 90 mm diameter in a year. The tumour volume doubling time was calculated to be 17 days.