We investigated 610 endoscopy-associated and 486 gastroenterology-associated malpractice claim files of the Physicians Insurers Association of America data-sharing project. We determined the relative malpractice claim risk for each of the major types of endoscopic procedures by comparing claim frequencies with Medicare performance frequencies. Relative malpractice risks were 1.0 for sigmoidoscopy, 1.2 for esophagogastroduodenoscopy, 1.6 for endoscopic retrograde cholangiopancreatography, and 1.7 for colonoscopy. "Improper performance" was alleged in 54% of claims and "diagnosis error" in 24% of claims. Of 121 claim files alleging a diagnostic error, 74 (61%) pertained to missed malignancies, of which 69% were colorectal. Of 147 claims alleging iatrogenic injury, 140 (95%) involved perforation or similar direct injury to the gastrointestinal tract. Problems with consent were alleged in 44% of 158 endoscopy-related claim files alleging additional associated issues.