A 58-year-old woman was admitted to our hospital because of recurrent fever, severe cough and sputum. Chest radiological examinations showed diffuse reticulonodular opacities in both lung fields. Interstitial pneumonia with probable polymyositis was diagnosed. Serum surfactant protein (SP)-A, SP-D and KL-6, which are new interstitial lung disease markers, showed values significantly higher than cutoff levels. The markers increased more in parallel with the rapid development of respiratory insufficiency, CPK level, myalgia and proximal muscle weakness. Treatment with a high dose of corticosteroid and the following gradual decrease over 8 months led to clinical and radiological improvement, with normalization of values of the markers. These markers may therefore be reliable indicators of therapeutic success. However, these markers underwent different respective changes during the first 2 months. SP-A reached a maximum at the start of the treatment, while SP-D and KL-6 peaked at 5 and 10 days, respectively, after the treatment was initiated. This discrepancy demonstrates that the markers reach the bloodstream by diverse mechanisms and are useful for analyzing pathophysiological alterations in the lung in the early stages of treatment.