The reviews demonstrate that, while much valuable work has been accomplished, there is considerable potential for further development of techniques, the utilisation of a wider range of techniques and a need for validation and evaluation of existing methods which would make incident investigation more versatile and use limited resources more effectively. Further exploration of techniques used in high-risk industries, with interviews and observation of actual investigations should prove valuable. Existing healthcare techniques would benefit from formal evaluation of their outcomes and effectiveness. Studies should examine depth of investigation and analysis, adequacy and feasibility of recommendations and cost effectiveness. Examining implementation of recommendations is a key issue.