Although most diagnostic GI endoscopic procedures in Germany are performed on an outpatient basis, there is no large-scale prospective evaluation of complication rates. Ninety-four gastroenterologists and internists from all regions of Germany recorded the number of EGD, colonoscopies, and polypectomies performed over a period of 1 year. All serious complications occurring in relation to the procedure, including the use of medication, were recorded in a structured protocol. A total of 110,469 EGDs, 82,416 colonoscopies, and 14,249 polypectomies were evaluated. The "reach-the-cecum-rate" was 97% (median). The overall complication rates for EGD, colonoscopy, and polypectomy were low compared with published data (0.009%, 0.02%, and 0.36%, respectively). The perforation rates were 0.0009%, 0.005%, and 0.06%, respectively, the rates of significant hemorrhage 0.002%, 0.001%, and 0.26%, respectively, and the mortality rates 0.0009%, 0.001%, and 0.007%, respectively. The rates of cardiorespiratory complications associated with EGD and colonoscopy were 0.005% and 0.01%, respectively. The overall complication rate for all procedures (diagnostic and therapeutic) was lower for gastroenterologists (1 per 5155 procedures) than internists (1 per 1539 procedures). Most of the adverse events associated with diagnostic endoscopy were attributable to use of medication. The severity score ranged from 2 to 5 for most of the adverse events occurring as a result of diagnostic procedures and 2 to 50 for polypectomy. The severity sum score per 10,000 procedures was 26 for EGD, 67 for colonoscopy, and 1185 for polypectomy. Outpatient endoscopy performed in practice settings by German gastroenterologists and internists is safe. The low complication rates may partly be explained by the high degree of experience resulting from the larger numbers of procedures performed relative to the numbers performed by gastroenterologists in hospitals and in other countries.