The prognostic value of DNA ploidy was evaluated in 25 patients with primary gastric leiomyosarcoma, using paraffin-embedded archival specimens analysed by DNA flow cytometry. Ploidy patterns were diploid in ten tumours and non-diploid in 15. They did not correlate with clinicopathological features of the lesions such as tumour size and grade or mitotic index. A non-diploid pattern was associated with a significantly reduced patient survival rate (P < 0.05), as was higher tumour grade (P < 0.01). Neither tumour size nor mitotic index correlated with patient survival.