Cytofluorometric analysis of FCM-DNA ploidy also seems to have prognostic value in prostatic carcinoma. Determination of the DNA index preoperatively from needle biopsy samples would be advantageous since it would enable the type of intervention to be established in advance. The finding of intratumoural variability in the DNA index in different solid tumours prompted us to compare the data obtained from needle biopsy and surgical specimens of prostatic cancer. Although the results obtained confirmed the heterogeneity of DNA content in prostatic carcinoma, they nonetheless indicate that preoperative DNA analysis is useful, in particular when aneuploidy is observed, since it provides the clinician with additional information on which to base treatment decisions.