From 1980 to 1993, the Danish Radio Medical Advice Service (RMAS) had 1136 contacts from overseas Danish merchant ships and 213 contacts from Danish territorial waters. The diagnoses were almost always of acute conditions. The distribution of the diagnoses in the overseas contacts were; diseases in the digestive and genitourinary system 30%, traumatic lesions 23%, infectious diseases 14% and diseases in the cardiovascular and respiratory system 9%. The only trend over the years was a significant (P = 0.01) decrease in psychiatric diagnosis. Evacuation from the ship was recommended in 53% and medicine was prescribed in 61% of the contacts. The medicine was antibiotics in 40% and analgesics in 29% of the contacts. Intravenous infusion was evaluated as relevant in 5% of the cases and this procedure will be included in the new education of officers on the ships. In the contacts from Danish territorial waters, where many ships are recreational yachts, evacuation was recommended in 79% and medicine was prescribed in 28% of the contacts. This was probably due to the short distance to the nearest harbour and the variation in medical equipment and knowledge. The medical speciality for doctors participating in RMAS should be general surgery or orthopaedic surgery but access to advice from all other medical specialities should be available. Experience as a naval medical officer would be beneficial. The education of the officers on the ships should be more comprehensive including e.g. intravenous infusion. Communication should be by telephone and television would be an advantage.