Acute pancreatitis is an unusual but recognized complication of percutaneous aspiration biopsy of the pancreas. As the pancreatic tail is located anterior to the left adrenal gland, percutaneous biopsy of a left adrenal mass via the anterior approach may result in needle passage through the tail of the pancreas with subsequent potential development of pancreatitis. To evaluate this risk, we retrospectively reviewed 48 CT-directed percutaneous aspiration biopsies of left adrenal masses done between 1984 and 1989 at two institutions. Positioning of the patient, the course of the needle, the number of needle passes, and the size of the needle were analyzed. Thirty-three (69%) of 48 biopsies of a left adrenal mass were performed by using the anterior approach. The pancreas was traversed by one or more needles in 32 of 33 cases. Biopsies were performed with 20- to 22-gauge needles, and the number of needle passes varied widely. The medical records of the 33 patients in whom the anterior approach was used also were reviewed for complications. Acute pancreatitis, which required 11-13 days of hospitalization, developed in two patients (6%). None of the other 31 patients suffered a complication. We conclude that the pancreatic tail is routinely traversed by the biopsy needle when biopsy of a left adrenal mass is done via the anterior approach and that severe acute pancreatitis can occur as a result.