Fifty-nine patients with pleural abnormalities on chest radiographs were evaluated by B-mode ultrasonography; the lesions were categorized as echo-free or complex. Echo-free lesions included pleural fluid collections, and abnormalities which did not yield "fluid" through an appropriately positioned large caliber needle. "Complex appearing" lesions yielded fluid through a needle in all cases. Ultrasonography could not accurately predict which lesions were amenable to successful thoracocentesis. Findings from recent radiographs and clinical history must be known when the ultrasonographic findings in patients with chest abnormalities are interpreted.