The evolution of in-depth research studies in Europe is reviewed, with particular emphasis on work in Britain since the early 1960's. The catalytic role of the NATO-CCMS programme in establishing in-depth teams in a number of countries and in developing common methodologies, notably in crash and injury severity, is outlined. The methodology of in-depth studies currently being conducted at the Accident Research Units at Birmingham University and at the Institute for Consumer Ergonomics at Loughborough is outlined and some observations are made on data collection techniques, analysis and project management.