A 59-year-old man was admitted to our hospital because of dyspnea. Chest radiography showed infiltration and consolidation in both lung fields. He was clinically diagnosed as having idiopathic interstitial pneumonia (IIP), and histological examination of a thoracoscopic lung biopsy specimen showed nonspecific interstitial pneumonia (NSIP) group 1. Corticosteroid therapy had previously been effective, but about 1 year later the disease recurred. The patient's clinical condition was very similar to the first episode, and is improving in response to the same treatment again. Although it is generally accepted that patients with IIP diagnosed histologically as NSIP have a good prognosis, it should be remembered that recurrence is possible, even in patients with group 1.