Inclusion criteria:  Referral to pulmonary services for large-volume thoracentesis  Presence of a symptomatic moderate or large free-flowing (non-septated) pleural effusion on the basis of:  Chest radiograph: effusion filling ≥ 1/3 the hemithorax, OR CT-scan: maximum AP depth of the effusion ≥ 1/3 of the AP dimension on the axial image Age >/= 18  Exclusion criteria:  Inability to provide informed consent  Study subject has any disease or condition that interferes with safe completion of the study including:  Coagulopathy, with criteria left at the discretion of the operator Hemodynamic instability with systolic blood pressure <90 mmHg or heart rate > 120 beats/min, unless deemed to be stable with these values by the attending physicians Pleural effusion is smaller than expected on bedside pre-procedure ultrasound Referral is for diagnostic thoracentesis only Presence of more than minimal septations and/or loculations( more than 3) on bedside pre-procedure ultrasound Inability to sit for the procedure