We investigated the DNA ploidy patterns in thirteen primary and four recurrent rhabdomyosarcomas of the head and neck from thirteen adult patients and correlated the findings with other clinicopathological factors and clinical outcome. Twelve (92.7 per cent) of the primary neoplasms manifested an aneuploid DNA pattern, five had more than one stemline, and one neoplasm displayed a diploid DNA pattern. All recurrent lesions were DNA aneuploid with DNA indices (DIs) corresponding to their primary neoplasms. No correlation between the ploidy pattern and histological subtypes, tumour location, clinical stage and patient's clinical course was found. In this study, only two patients were long-term survivors. Both patients had stage I neoplasms that were located in non-parameningeal sites which manifested an alveolar histological pattern. Our data indicate that adult rhabdomyosarcomas of head and neck are preponderantly DNA aneuploid and are highly aggressive malignant neoplasms. Our results also suggest that tumours which are low stage and in a non-parameningeal location may pursue a less aggressive course.