Lymphoid interstitial pneumonia (LIP) is a rare entity characterized by the infiltration of interstitial tissues and alveolar spaces by lymphocytes, plasma cells, and other lymphoreticular structures. The etiology of LIP is unknown, although associations with autoimmune and infectious factors have been described. The incidence of LIP has risen in recent years, mainly in children with acquired immunodeficiency syndrome (AIDS), while remaining less common in the adult population. No agreement has been reached regarding the diagnostic tests necessary for a firm diagnosis although suspicion is usually based on clinical and radiographic findings, with confirmation provided by examination of histological samples. The most common treatment is corticosteroids, either alone or in combination with other immunosuppressant agents although no evidence from controlled trials is available and cases have been reported in which LIP resolved in AIDS patients with antiretroviral therapy alone. We report the case of a human immunodeficiency virus-infected adult who was diagnosed with LIP by open lung biopsy and who responded to antiretroviral drugs with no need for associated corticosteroid therapy.