Lymphocytic interstitial pneumonia is at present a pathologic diagnosis. In the setting of a chronic interstitial pneumonia in a child with lymphocytosis, hyperglobulinemia, and lymphadenopathy or parotid enlargement, the diagnosis is often clinically presumed. At present the diagnosis can be established firmly only by lung biopsy. Models of pathogenesis include nonspecific stimulation of the immune system, HIV-specific stimulation, or synergy between EBV and HIV. Treatment includes oxygen and bronchodilators as needed. The role of zidovudine and of steroids in the management of LIP remains to be determined.