We investigated the relationship between DNA ploidy and the prognosis of pheochromocytoma. DNA ploidy studies on paraffin-embedded archival specimens from ten cases of pheochromocytoma were performed by flow cytometry according to Hedley's method. Clinical features and pathological results were investigated and follow-up was made. The values of DNA content in assessment of the prognosis of the tumor were discussed. Flow cytometry examination showed that seven cases had aneuploid, two deploid and one tetraploid. The malignent case was tetraploid, and died from matastasis to the bone. The other cases had a benign process. The examination of DNA content is of value in the assessment of the prognosis of pheochromocytoma.