A cohort of 1455 sea pilots and boatmen employed after 1921 was established. Those identified and alive in 1951 (n = 1323) were linked to the Swedish cause of death register 1951-84. In 21 352 person-years 383 deaths were observed among sea pilots compared with 379.3 expected (SMR = 101;95% CI between 99 and 112) and in 12,127 person-years the observed number of deaths among boatmen was 136, expected 135.9 (SMR = 100) when Swedish men were used as a reference population. For ischaemic heart disease (IHD) (ICD-8: 410-414) the SMR was equal to 96 (obs = 131, exp = 137.2) for sea pilots and 91 (obs = 44, exp = 48.4) for boatmen. No trend over time or geographical differences could be observed. A healthy worker effect could not explain why there was no excess mortality from IHD.