We investigated the DNA ploidy patten in thirteen primary and four recurrent rhabdomyosarcomas of teh head and neck from thirteen adult patients and conrrelated the findings with other clinicopathological factors and clinical outcome. Twelve (92.7 per cent) of the primary neoplasms manifested an aneuploid DNA pattern. All recurrent lesions were DNA aneuploid with DNA indices (DIs) Corresponding to their primary neoplasms. No correlation beteween the ploidy pattern and histological subtypes, tumours 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-parameninigeal sites which manifested an alvellar histological pattern. Our data indicate that adult rhabdoyosarcomas of adult and neck are preponderantly DNA aneuploid and are highly aggressive malignant neoplasms. Our results alson suggest that tumours which are low stage and in a non-parameningeal location may pursue a less aggressive course.