Complications in trauma care occur because of provider-related or patient disease-related events, Strictly defined standardized definitions of both types of complications are needed to develop strategies for problem resolution. The frequency and characteristics of 135 disease-related and provider-related complications were examined for a 3-year period in a level I university trauma service in all patients meeting Major Trauma Outcome Study (MTOS) criteria. Provider-related complications were analyzed for recurrent process errors to be targeted for corrective action. Complication events occurred in 2764 of 3327 patients, with provider-related complications in 759. Twenty-three percent (175) of complications were judged unjustified and 16 patterns of recurrent process-of-care errors were identified. Delay in trauma team activation was caused by insensitivity of field triage protocols and inadequate recognition of injury patterns. Delays in diagnosis or surgery were caused by inadequate performace of standard work-up, inadequate recognition of injury severity by providers, diagnostic procedure interpretation errors errors in prioritizing the order of diagnositic procedures. Errors in technique were attributed to inexperience, haste, unfamiliarity with devices, lack of developed institutional techniques failure of providers to use recognized endpoints. Errors in judgement were attributed to failure to access available patient information, proceeding despite available information failure to utilize available care guidelines. Further reduction in provider-related morbidity in an organized trauma system requires this type of analysis, which identifies the need to change the process of care through education or adjustment of protocols for standardized care delivery in addition to the traditional focus on outcomes.