BACKGROUND: In the adult, the primary infection by the varicella-zoster virus acquires an unusual severity due to several complications, the most frequent of them being pneumonia. We study the main characteristics of nine patients diagnosed of pneumonia varicellosa. METHODS: Clinical, therapeutic and evolutive features of 9 adult patients, both immunocompetents and immunodepressed, diagnosed of pneumonia varicellosa are retrospectively reviewed, in the last ten years, at Hospital de Sant Pau, Barcelona. Diagnosis of varicella was established on the basis of the typical rash in the context of a feverish illness. The antecedents of smoking habit, pregnancy and underlying disease, evaluating especially arterial blood and platelet count at entrance, are assessed. RESULTS: Nine patients (4 males and 5 women; mean age 38 years) were included in the study. Seventy-eight percent of patients were smokers of more than 20 cigarettes a day; one met criteria of simple chronic bronchitis, another suffered ankylosing spondylitis and three were known carriers of human immunodeficiency virus. None of the female patients was pregnant. Respiratory symptoms began from the third and fifth day after the skin rash, and the most common symptoms were cough (89%), dyspnea (67%) and hemoptysis (22%). Arterial blood gas determination showed hypoxemia in four patients (45%). Chest X-ray revealed an interstitial pattern predominantly at both bases, with a case of right pleural effusion. Intravenous acyclovir was started in 6 patients, foscarnet in one and symptomatic therapy in two patients. All patients had a favourable clinical course, none of them requiring entrance to the Intensive Care Unit. CONCLUSIONS: Adult patients with varicella pneumonia that suffer respiratory insufficiency, thrombocytopenia or are carriers of base illnesses must be early treated with intravenous acyclovir. However, despite clinical, biological and radiological recovery is earlier with such treatment, the evolution seems equally favourable if it is only conducted, for instance, symptomatic therapy with antithermic and antihistaminic compounds.