The Pneumoconiosis Research Unit (PRU) was set up to obtain the information needed to eliminate pneumoconiosis of coal workers. To this end, instruments and procedures were developed for dust sampling, delivering dust to animals, testing lung function, reading chest radiographs, conducting respiratory surveys and extracting the relevant information. A provisional estimate of safe working conditions was made using data from four pits. The National Coal Board extended the research to an additional 20 pits, refined the estimate and applied it nationally. Meanwhile at PRU aspects of treatment were explored, immunological techniques were added to the repertoire of skills, other occupational disorders were highlighted and new information obtained on biological variation in lung function and blood pressure. The work laid the foundations for medical epidemiology and evidence-based medicine. Starting in 1959, the Unit took the lead in a world campaign to control lung diseases due to asbestos. This account indicates how these successes were achieved, what were the failures, some tensions which developed and what might have been if some events had been handled differently. If there is a message, it is that for success in research the problem under consideration should be the prime focus of attention and resources.