A device was designed to facilitate placement of biopsy needles with computed tomographic guidance. The device consists of a hollow, clear plastic disk filled halfway with fluid and a central stem with a groove for the needle. When the device is rotated, the air-fluid level points to the corresponding angle marked on the side of the disk. In a phantom study, 17 of 20 passes were within +/- 3 degrees of the anticipated angle of entry, and the remaining three were within +/- 5 degrees. The device was also used in 14 patients; the resultant angle of entry was within +/- 3 degrees of the anticipated angle.