Second primary tumours occur frequently in patients with a history of head and neck malignancies. Delays in making an early and correct diagnosis can seriously affect the therapy management and survival. This was a retrospective study of 120 patients with a history of head and neck cancer, presenting with a second primary tumour. Current follow-up strategies and the use of routine sonographic imaging of the head and neck regions were evaluated, and the impact that tumour chronology, the tumour site and the various treatment modalities have on the survival were assessed. Forty-two per cent of patients developed a metachronous second malignancy more than five years after diagnosis of the index tumour. The accuracy of colour-duplex sonography in detection of second primaries in the head and neck was 82.3 per cent. First and second primary tumours located in the larynx were observed to have the highest five-year survival rate. Patients who developed metachronous tumours had a five-year survival rate of 68.9 per cent for the index tumours, and a 26 per cent five-year survival rate with the occurrence of a second neoplasm. With synchronous tumours a mean survival time of 18 months and a five-year survival rate of 11.9 per cent was found (p < 0.0001). Where clinically appropriate an aggressive treatment strategy was employed and yielded the most favourable results with a five-year survival rate of 66.8 per cent and 35.9 per cent for index tumours and second primary malignancies, respectively. Since more than 40 per cent of the metachronous second primaries in patients with a history of head and neck malignancy occur beyond the five-year follow-up period, an extended protocol with individually adjusted close monitoring of high-risk patients seems appropriate. Colour-duplex sonography is a valuable screening investigation for the early detection of second primary tumours. The treatment of a second primary is often less successful than for the same malignancy occurring primarily. The prognosis of synchronous tumours is significantly lower when compared to malignancies of a metachronous nature, despite some encouraging individual results. Only the early implementation of aggressive treatment methods for second primaries is successful in terms of survival.