In the period 1986-1988 a prospective study comprising 30 crew members of deep-sea factory-trawlers (altogether 2468 fishermen) and 85 of the merchant navy vessels (total 2906 seafarers). At least one chronic ailment or a deviation from the norm was found in 32.5% of fishermen and in 45.4% of seafarers. On the average the seafarers were older than their counterparts fishermen by 2 years and 2 month. Traumas, fractures, wounds and injuries were the most often, the prevailing reason for the sick absence (619 days sick absence per 1000 fishermen and 1075 days sick absence per 1000 seamen annually). The most frequent in fishermen were: acute infections of the respiratory tract, skin diseases, diseases of the oral cavity and teeth, diseases of the articulations. The diseases of a highest prevalence in seafarers were: acute infections of the respiratory tract, diseases of the oral cavity and teeth, skin diseases, gastritis and duodenitis. There were noted 27 serious ailments and 9 accidents requiring repatriations on shore and home in fishermen and 18 such diseases and 21 accidents in seafarers.