DNA analysis by flow cytometry has been reported to be a useful prognostic technique for a variety of malignant tumors. The goal of this study was to examine DNA ploidy status and proliferation index as potential predictors of recurrence and survival for patients with squamous cell vulvar carcinomas. The DNA ploidy, percentage of cells in the S-phase of the cell cycle, stage, and histologic grade were analyzed in 42 patients. Flow cytometry was performed on archival paraffin-embedded tissue. The histologic specimens were reviewed by a single pathologist. Thirty-four tumors (81%) were diploid and eight (19%) demonstrated an aneuploid peak. The percentage of cells in the S-phase (proliferation index) was calculated for all patients. The 5-year survival rate was 68% for diploid tumors and was 75% for aneuploid tumors. The difference between these rates was not statistically significant (P < or = 0.65). S-phase fraction was also not a useful predictor for recurrence or overall survival. FIGO stage and histologic grade were accurate predictors for both recurrence and 5-year survival. Multiple predictor analysis using stage, grade, ploidy status, and proliferation index did not identify any subgroup which would predict recurrence better than FIGO stage and grade. DNA ploidy and S-phase fraction analysis do not appear to be clinically useful prognostic factors for vulvar squamous cell carcinomas.