The relationship between DNA ploidy and prognostic parameters has been established in prostate cancer. However, comparison of various techniques used for DNA ploidy analysis has not been sufficiently addressed in prostate carcinoma. In the present study, grossly identified discrete carcinoma foci from 48 consecutive radical prostatectomy specimens were analyzed by flow cytometry and image analysis using both imprints and tissue sections. Correlations with other prognostically important pathological findings such as grade, size, extracapsular extension, positive surgical margin, and seminal vesicle and lymph node involvement were done. Image analysis detected 26 (54.2%) nondiploid tumors compared to 15 (31.3%) nondiploid tumors by flow cytometry. No significant differences were demonstrated between imprints and tissue sections. DNA ploidy status showed a good correlation with most other pathological findings listed above. In conclusion, DNA ploidy status determination gives clinically useful information which correlates well with the other useful pathological parameters of prognostic importance. Image analysis may be more sensitive than flow cytometry in detecting nondiploid populations. Tissue sections appear to be as reliable as imprints when properly controlled.