OBJECTIVE--To investigate whether fatal accidents, including drownings, have decreased among Icelandic fishermen and seamen. DESIGN--Historical prospective study. The study population was record linked with the National Register and the Register of Deceased to get information on water transport accidents (ICD-7, E850-E858) during the period 1966-86. The number of persons in each calendar year and the number of days at sea registered at the pension fund were both used as denominator to find annual mortalities. SETTING--Iceland. SUBJECTS--27,884 seamen who were members of the Seamen's Pension Fund. The cohort included both fishermen and seamen from the merchant fleet. MAIN OUTCOME MEASURES--Changes in mortality from all accidents and drownings from 1966-86. RESULTS--The mortality for all fatal accidents was 89.4 per 10(5) person-years and did not change appreciably during the study period. The mortality for drowning was unchanged at 73.2 per 10(5) person-years. The greatest number of drownings were among those 20-24 years of age but the mortality for drowning was highest among those 45-54 years of age. CONCLUSION--Mortality because of fatal accidents and drownings among these seamen was high and did not conclusively decrease during the study period. Further preventive measures are needed.