Objective. Effects of high frequency chest wall oscillation technique were investigated on intubated ICU patients. Background. Thirty intubated patients were included in the study. The control group (n = 15) received routine pulmonary rehabilitation technique. In addition to the pulmonary rehabilitation technique, the study group (n = 15) was given high frequency chest wall oscillation (HFCWO). APACHE II, dry sputum weight, lung collapse index, and blood gas values were measured at 24th, 48th, and 72nd hours and endotracheal aspirate culture was studied at initial and 72nd hour. The days of ventilation and days in ICU were evaluated. Results. There is no significant difference between APACHE II scores of groups. The dry sputum weights increased in the study group at 72nd hour (p = 0.001). The lung collapse index decreased in study group at 48th (p = 0.003) and 72nd hours (p < 0.001). The PO2 levels increased in the study group at 72nd hour (p = 0.015). The culture positivity at 72nd hour was decreased to 20%. The days of ventilation and staying in ICU did not differ between the groups. Conclusions. Although HFCWO is very expensive equipment, combined technique may prevent the development of lung atelectasis or hospital-acquired pneumonia more than routine pulmonary rehabilitation. It does not change intubated period and length of stay in ICU. However, more further controlled clinical studies are needed to use it in ICU.