Closed suction catheters (CSC) for removal of bronchial secretions in intubated patients have been used in intensive care units (ICU) for many years. Manufacturers still recommend daily changes of the catheter in order to reduce the incidence of ventilator associated pneumonia (VAP). There is, however, a lack of clinical evidence to support this recommendation. The objective of this study was therefore to compare the incidence of VAP in patients who receive either 24 hourly or 48 hourly changes of the CSC. Eligible patients were randomised to one of the two groups to receive either a 24 hourly change (n = 53) or a 48 hourly change (n = 48) of the CSC. Sputum specimens were sent second daily for quantitative culture. Chest x-rays (CXR) and white blood cell counts were attended daily. A VAP was diagnosed according to previously established criteria. A second set of modified criteria were also used to conduct a further analysis of the results. Of the 158 patients randomised, 101 completed the study. These patients had a mean age of 65 years and a mean APACHE II score of 28.2 in the first 24 hours of the study. The average duration in the trial was 10 days. The two groups were comparable in terms of demographic features. There were no reported cases of VAP in either group using the criteria originally selected in the study design. Using a modified criteria to diagnose VAP there were 10 (19%) patients with VAP in the 24 hour group and 13 (27%) in the 48 hour group. The incidence of VAP between the two groups was not statistically different (p = 0.35). To conclude, there was no difference in the incidence of VAP between the two groups studied. Based on previous studies conducted by Quirke and Kollef and the experience of our study we have changed our clinical practice to a 48 hour change of the CSC. We would, however, suggest further study or a meta-analysis of the available literature before a recommendation is made.