Thoracostomy tube drainage with tetracycline (TCN) instillation is an effective technique for management of recurrent, symptomatic, malignant pleural effusions. Although patient rotation through various positions after instillation of TCN has been advocated empirically, it has not been shown scientifically to be necessary and is often uncomfortable for the patient and time-consuming for personnel. Five patients with symptomatic, malignant pleural effusions were studied during pleurodesis using radiolabelled TCN. Scintigraphic imaging was done immediately after TCN instillation prior to patient rotation. Patients were rotated through six positions and multiple images were obtained at 30 and 120 minutes. Tetracycline dispersed throughout the pleural space within seconds. Patient positioning had no effect on the intrapleural distribution of TCN in four of the five patients. In one patient with loculated hydropneumothorax and trapped lung, rotation minimally improved distribution of TCN to the apex. Rotation during pleurodesis does not appear to be necessary in patients with a relatively normal pleural space. However, patient rotation enhances distribution of TCN when the lung is separated substantially from the chest wall, as with trapped lung. Possibly, in this situation the properties of fluid mechanics and capillary action no longer apply.