Over the last two years we have conducted research on the costs of accidents in the workplace, monitoring 14 firms in the Republic of Ireland (RoI) over a 12 week period in 1995, and 11 firms in Northern Ireland (NI) over a 12 week period in 1996. Using a standard Report Form (Appendix I) which was filled in by the appropriate manager for every accident over the period, we have been able to obtain interesting case study information on the nature of the costs of accidents. In this paper we discuss costs of accidents in general (Section II), then describe our research methodology (Section III). The next section, section IV, presents the information on the costs of accidents arising from the research, in three sub-sections: total costs, direct vs indirect costs, and insured vs uninsured costs. In section V, we briefly summarise some of the recent literature on the prevention of accidents. Finally, section VI provides a brief conclusion.