To analyze the system factors related to "line, tube, and drain" (LTD) incidents in the intensive care unit (ICU). Voluntary, anonymous Web-based patient safety reporting system. Eighteen ICUs in the United States. Incidents reported by ICU staff members during a 12-month period ending June 2003. None. Characteristics of the incidents (defined as events that could/did cause harm), patients, and patient harm were described. Separate multivariable logistic regression analyses of contributing, limiting, and preventive system factors for LTD vs. non-LTD incidents were reported. Of the 114 reported LTD incidents, >60% were considered preventable. One patient death was attributed to an LTD incident. Of patients experiencing LTD incidents, 56% sustained physical injury, and 23% had an anticipated increased hospital stay. Factors contributing to LTD incidents included occurrence in the operating room (odds ratio [OR], 3.50; 95% confidence interval [CI], 1.25-9.83), occurrence on a holiday (OR, 3.65; 95% CI, 1.12-11.9), patient medical complexity (OR, 3.68; 95% CI, 2.28-5.92), and age of 1-9 yrs (OR, 7.95; 95% CI, 3.29-19.2). Factors related to team communication were less likely to limit LTD incidents (OR, 0.28; 95% CI, 0.11-0.68), while clinician knowledge and skills helped prevent LTD incidents (OR, 1.80; 95% CI, 1.09-2.97). Patients are harmed by preventable LTD incidents. Relative to non-LTD events, these incidents occur more frequently during holidays and in medically complex patients and children. Focusing on these contributing factors and clinician knowledge and skills is important for reducing and preventing these hazardous events.