In 1984, during 201 voyages of cargo ships of Polish Ocean Lines having doctors on board, 30340 medical consultations were given to crew members, in 15506 cases of complaints and diseases. Doctors also consulted injured seafarers 2456 times in cases of injuries, wounds, contusions, broken bones, burns, scalds etc. During these 201 voyages, 33 cases of serious medical conditions were reported among crew members, which required disembarkation and hospital treatment abroad; in this number two cases of myocardial infarction ended fatally. There were also 13 casualties among seamen, which were treated in hospitals in foreign ports; all of them survived. One of the important health problems of seafarers were diseases of teeth, pulp, and periapical tissue. Such cases constituted the majority (66.9%) of all 1868 cases referred for consultation and treatment in foreign ports. Oral diseases prevention among seafarers needed improvement. The working time of doctors on board ship was under-utilized. To a greater extent they should be involved in training seafarers in first aid and primary health care, and in health education activities among seamen, during sea voyages. Materials presented in the paper may be of use in planning efficient and cost-effective health services for crews of ships.