The clinical, laboratory, and ultrasonographic findings in children receiving L-asparaginase therapy were retrospectively reviewed and correlated to determine the diagnostic reliability and clinical usefulness of serial pancreatic sonograms in detecting L-asparaginase-induced pancreatitis. A total of 217 sonograms were obtained in 92 patients. Six of the 92 (6.5%) had L-asparaginase-induced pancreatitis. The diagnosis of pancreatitis was based solely on clinical symptoms in three patients, on clinical and laboratory findings in two, and on sonographic and laboratory findings in one. No confirmed cases of pancreatitis were detected solely by ultrasonography before clinical or laboratory evidence was obtained. Sonograms were useful only in confirming clinical and/or laboratory evidence of pancreatitis, but were of no value in making the early or preclinical diagnosis of drug-induced pancreatitis. We have discontinued the practice of obtaining routine serial pancreatic sonograms in children receiving L-asparaginase at our institution.