The Macondo well blowout resulted in 11 fatalities and caused the largest nonintentional oil spill in history. The situation stemmed from a series of human errors through all stages of the project leading up to the blowout and subsequent explosion. These errors include faulty interpretation of signals indicating problems with well and safety system integrity, inappropriate modifications to safety systems, inadequate design of critical systems, failure to provide redundancy in the design stage, failure to adhere to administrative controls for the safe operation, failure to follow the American Petroleum Institute Recommended Practices 75 on drilling mud circulation, and others. Twenty five specific errors have been identified and classified into eight categories. The results show that the majority of the errors are latent errors and caused by poor leadership in the organization or management. In order to resolve these issues it is necessary to create a safety culture in which safety is paramount in operations and facilities. There are many lessons learned from this incident, but the most important lesson is that safety must be a way of life, beginning in the design stage and carrying through the project life cycle. (c) 2013 American Institute of Chemical Engineers Process Saf Prog 32: , 2013