Ventilator-associated pneumonia is the most frequent nosocomial infection in intensive care units (ICU) and causes high mortality. Approximately 50% of all antibiotics in ICUs are administered for the treatment of respiratory tract infections. Prompt and appropriate antibiotic treatment is paramount for a favourable clinical outcome as any delay in diagnosis and treatment will result in increased mortality. Therefore it is common practice in many ICUs to perform routine surveillance cultures of lower respiratory tract samples so that when pneumonia occurs, the empiric antibiotic regime can be based on the pathogens previously identified in surveillance cultures. This article highlights the advantages and disadvantages of routine surveillance cultures and provides a critical review of the recent literature. The majority of published studies favour surveillance cultures, because these can often predict the pathogens responsible for pneumonia and lead to timely administration of adequate antimicrobial therapy. Although the rationale behind this approach appears evident, the impact of surveillance cultures on clinical outcome as well as their cost effectiveness remains to be determined. Therefore, at this point, national and international guidelines do not recommend the routine use of surveillance cultures in mechanically ventilated patients but stress the need for larger, well designed clinical studies.