In the 1980s, nosocomial pneumonia became the second most common nosocomial infection in the United States. Gram-negative bacilli and Staphylococcus aureus were the most frequently isolated bacteria. Methods to improve the diagnostic sensitivity and specificity included transtracheal aspirates and bronchoscopy with protected specimen brush or bronchoalveolar lavage. Multivariate analysis was used to identify independent risk factors for pneumonia and fatality in different subsets of high-risk patients. Gastric pH and colonization were evaluated as risk factors for pneumonia in mechanically ventilated patients. Colonized respiratory therapy equipment and contaminated tubing condensate and in-line medication nebulizers were suggested as possible sources of nosocomial pathogens. Staff education programs, the use of barrier precautions, and selective decontamination of the digestive tract were associated with reduced rates of lower respiratory tract infection. Despite a decade of progress in our understanding of nosocomial pneumonia, progress in the 1990s will undoubtedly include molecular epidemiologic techniques, appropriate application of risk factor data, and the use of new methods for the diagnosis of pneumonia. Prevention strategies should focus on more effective infection control techniques, improved invasive devices/equipment, and the judicious use of antibiotics for treatment and prophylaxis.