The interstitial lung diseases (ILD) are a diverse group of lung disorders that involve primarily the parenchyma of the lung. Whether idiopathic or secondary to systemic disorders, inhaling exposures, or drugs, they inflame and scar the interstitium of the lungs and obliterate alveoli and capillary units. The scarring or fibrosis produces restrictive lung impairment while destruction of the alveoli, interstitium, and capillaries results in severe gas exchange abnormalities. Clinically, the ILD present subtly with progressive dyspnea on exertion and a dry cough. Rales or crackles on examination prompt chest radiography that may reveal bilateral infiltrates. These infiltrates are often treated as atypical pneumonias that fail to respond to antimicrobial therapy over weeks to months. Because of this and their infrequent presentation in the primary care setting, the diagnosis of ILD is commonly delayed. This paper highlights the natural history of the ILD in general, gives a broad overview of the pathophysiology in these diseases, and encourages greater awareness for the detection of ILD in primary care.