A total of 657 boat refugees from Vietnam who came to Denmark during a three-month period in autumn 1979 were submitted to health examination immediately on arrival. The commonest conditions were intestinal parasitosis (63%), skin infections (27%) and infections in the upper respiratory tract (14%). Approximately 11% were HB(s)Ag carriers, less than 10% had pathogenic intestinal bacteria, 1% excreted Poliovirus and 1% had open pulmonary tuberculosis. Malaria was found in 4%. But tropical diseases were rare. 36% had eosinophilia which was usually due to intestinal parasites and approximately 3% had positive serological reactions for syphilis. The smooth running of this programme of investigation demanded considerable planning and administration. When the investigation and therapeutic programme was complete, the boat refugees did not appear to constitute any epidemiological threat for the Danish population.