Impairment of the state of consciousness is an important contributing factor in the onset of respiratory tract infections; in this study the data were collected prospectively to investigate the incidence and clinical implications of pneumonia in a population of head injured patients. The study was conducted on all patients treated at our centre throughout 1990. The incidence of pneumonia in the head injured was 10.8% versus 7.3% in the rest of the patients. Mortality in the group with pneumonia was not significantly different from the group without pneumonia. The average time of onset was on the fifth day from admission. The lung injury score (LIS) on the sixth day, the time on artificial ventilation and the length of stay in intensive care were significantly greater in those with pneumonia (1.18, 14.6 days and 21.9 days versus 0.8, 4.2 days and 12.9 days respectively). Staphylococcus was the single most frequently isolated germ. Our study concludes that pneumonia represents a relatively frequent and early complication in patients with head injury, and it is associated with prolonged artificial ventilation and longer staying in ICU.