A systems approach to accident investigation was applied to 338 underground mining accidents. A taxonomic model of contributing factors in accident causation was developed, and expert raters assessed the degree to which each factor played a role in each accident case. The model contained the following factors: management, physical environment, work task, equipment, social environment, perceptual-cognitive-motor (pcm) error of the injured employee and coworkers, worker characteristics of the injured employee and coworkers, and other miscellaneous factors. The report contains a literature review on the analysis and classification of human error, including the role of human error in accidents. Results indicated that 88 pct of the cases involved more than one causal factor. Injured employee pcm error was involved to some degree in 93 pct of the cases, and when involved, averaged about 33 (of 100) points of causality. The factor was considered a primary causal factor in almost 50 pct of the cases and a secondary causal factor in another 24 pct. Management was the second most important causal factor. It was considered a primary factor in 22 pct of the cases and a secondary factor in another 12 pct. Recommendations are presented and discussed.