The aim of this study was to investigate the most hazardous of all occupations in Great Britain. The causes of all deaths in British merchant seafaring and trawler fishing, traditionally the two most dangerous occupations, were established for the period between 1976 and 1995 and compared with official mortality statistics for other occupations. Fishermen were 52.4 times more likely to have a fatal accident at work (95% CI 42.9-63.8), and seafarers were 26.2 times more likely (19.8-34.7), compared with other British workers. Although the number of work-related deaths has decreased in recent decades, in relative terms the occupations of fishing and seafaring remain as hazardous as before. If mortality rates in these occupations are to decrease, unsafe working practices, especially unnecessary operations in treacherous conditions, should be reduced.