In an attempt to improve the investigation of the human factors causes of accidents in the UK offshore oil and gas industry, a Human Factors Investigation Tool (HFIT) was developed with the sponsorship of the UK Regulator, the Health and Safety Executive, and four exploration-related companies. The tool was developed on a theoretical basis with reference to existing tools and models and it collects four types of human factors information including (a) the action errors occurring immediately prior to the incident, (b) error recovery mechanisms, in the case of near misses, (c) the thought processes which lead to the action error and (d) the underlying causes. The investigation tool was evaluated on the basis of (i) an inter-rater reliability assessment, (ii) usability assessment, (iii) case studies and (iv) an evaluation system developed by Benner [Benner, L. 1985. Rating accident models and investigation methodologies. Journal of Safety Research 16, 105-126] Evaluation system. Although there is a need for further validation and analysis of HFIT using more realistic accident scenario exercises, some validation of the tool has been possible. In addition, it has been shown, in a small sample of accident investigations, that HFIT was found to be useful for the development of remedial actions, one of the main objectives of the tool. (c) 2005 Elsevier Ltd. All rights reserved.