Herpetic tracheobronchitis and pneumonia occur basically in immunodepressed patients, but have rarely been reported in patients with the acquired immunodeficiency syndrome (AIDS). Some large reviews on pulmonary manifestations in AIDS report a small number of herpetic pulmonary infections, without determining any prevalence of this particular viral involvement. Predisposing factors are alteration of cell-mediated immunity and invasive procedures (such as endotracheal tube use) in debilitated patients. The case we report illustrates the occurrence of a herpetic tracheitis in an HIV-infected patient with severe P. carinii pneumonia, needing systemic corticotherapy and mechanical ventilation. It illustrates the risk of dissemination of herpes simplex virus (HSV) from a herpetic stomatitis to the lower respiratory tract, even after the endotracheal cannula has been removed.