The authors analyzed two invasive procedures used to visualize the biliary tree, endoscopic retrograde cholangiopancreatography (ERCP) and percutaneous transhepatic cholangiography (PTC), and also explored the utility of preinvasive workups for patients with suspected cholestasis. For this analysis they used published ranges for success, fatality, complications, diagnostic accuracies of the procedures, and prognostic information about the underlying diseases. The choice between ERCP and PTC was found to be a "close call," but ERCP was generally favored as the first-choice procedure. The results suggest that noninvasive imaging does not help decide between ERCP and PTC. Although noninvasive imaging may identify those patients with common duct dilation, the higher success rate with PTC in these patients is offset by a slightly higher mortality rate. Consequently, the choice between ERCP and PTC remains close even if ultrasound has shown that biliary ducts are dilated. Furthermore, it is shown that these noninvasive tests are most useful when they can conclusively determine the presence or absence of biliary obstruction. For many patients, noninvasive imaging will not obviate the need for invasive tests.