In a prospective study, the value of the clinical follow-up after treatment for head and neck cancer has been assessed. A total of 407 visits in 377 patients were recorded during a three month period in 1993 at the two major radiotherapy departments in Denmark. The results showed that 61% of follow-up visits included one or more problems either related to treatment morbidity or tumour recurrence. About 50% of all visits included treatment related normal tissue problems, and 30% had problems that required intervention. Although the majority of problems occurred within a few years after treatment, 47% of patients at three to four years observation time still had one or more problems. A total of 34 new tumour recurrences were found in the period, and of these 11 (32%) were asymptomatic. It is concluded that head and neck cancer patients have both tumour and normal tissue problems several years after the end of treatment. Since effective salvage treatment improves local control significantly, early detection of possible recurrence is important. A follow-up period of four to five years is recommended-preferably by qualified experts in the management of both recurrent disease and treatment morbidity.