HUMAN ERROR ROOT CAUSE ANALYSIS (HERCA) started after a review of the data from DOE s Occurrence Reporting Processing System (ORPS). This review showed that about two-thirds of occurrences had human error listed as a cause. Considering procedures, training and man-machine interfaceare separate categories, this number jumps to over 95% of occurrences. A critical review of the human error category within ORPS showed no differentiation of human errors into components.Enhancement Process (HPES), the NRC's Human Performance Investigative Process (HPIP), INEL's HSYS, and the commercial TAPROOT system, it was concluded that human error can be divided into eight major categories of causes, with differentiation into specific causes within each of these major categories. It was decided to adapt NRC's accident analysis techniques to DOE.HERCA does not replace standard techniques such as MORT or REASON, it supplements them. Once a more standard accident analysis technique has identified a human performance deficiency as a component in the occurrence, then the HERCA technique can be used to help the investigator determine why the human error occurred. HERCA has two basic parts; 1) the decision tree which leads the user through a series of questions with answers directing him to 2) one of eight major cause categories which categorize and define the human error root cause. HERCA emphasizes task analysis for human error analysis but also uses standard accident analysis techniques (such as Event and Causal Factor charting, change analysis, and barrier analysis) to assist the investigator in determining the true cause of occurrences with human error.