BACKGROUND Use of metronidazole has been suggested to be associated with an increased risk of acute pancreatitis in case reports. AIM To examine this issue within a proper epidemiological design. METHODS We identified 3083 incident cases of acute pancreatitis from Hospital Discharge Registries in three Danish counties and 30 830 matched population controls. From prescription databases, we extracted information on use of metronidazole with or without concomitant use of proton-pump inhibitors and/or amoxicillin, macrolides or tetracycline. RESULTS Adjusted odds ratios for acute pancreatitis in study subjects who redeemed a prescription for metronidazole within 30, 31-180, or 181-365 days before hospitalization or index date among controls were 3.0 [95% confidence interval (CI): 1.4-6.6], 1.8 (95% CI: 1.2-2.9) and 1.1 (95% CI: 0.6-1.8), respectively. Among subjects with a concomitant prescription for proton-pump inhibitors and/or amoxicillin, macrolides or tetracycline within 30, 31-180, or 181-365 days before hospitalization, or index date among controls, adjusted odds ratios were 8.3 (95% CI: 2.6-26.4), 2.7 (95% CI: 1.4-5.5), and 1.7 (95% CI: 0.6-4.8), respectively. CONCLUSION Metronidazole may increase the risk of acute pancreatitis. However, the risk seems mainly to increase when metronidazole is used in combination with other drugs used for Helicobacter pylori eradication.