Idiopathic interstitial pneumonias (IIP) can be combined under the term "idiopathic fibrotic lung disease". It has a number of characteristic clinical and morphological features, which depend on the course of the disease (acute, subacute, or chronic) and are never identical in the early and end stages. Combining all types of IIP, other than unclassified interstitial pneumonias and cryptogenic organizing pneumonia, under the term "idiopathic fibrotic lung disease" will make it possible to move away from the ambiguous concept of so-called early diagnosis of idiopathic pulmonary fibrosis, establish criteria of disease activity, and identify clear indications for systemic corticosteroids and new antifibrotic agents in patients with IIP. Keywords: idiopathic interstitial pneumonias, idiopathic pulmonary fibrosis, early diagnosis, principles of treatment.