In this communication we present our preliminary evaluation of the utility of DNA cytometry in predicting clinical outcome of patients with resectable primary invasive ductal breast carcinoma. In 84 consecutive fresh frozen tissues samples, submitted for steroid receptor assay, we determined the DNA content following consensus guidelines for the routine clinical use of DNA cytometry. It has been possible to calculate the DNA index in all samples and for 5 "aneuploid" cases, SPF was considered unevaluable, because of a small proportion of tumour cells (<20%). 27 of 84 cases (32%) presented a DNA index of 1.0 ("diploid"). "aneuploid" tumours have a tendency for a less favourable prognosis [relative risk (RR) of recurrence =3.02 (95% ci: 0.88-10.4) and RR for mortality =1.70 (95% ci: 0.46-6.29)]. The relative number of "hypoploids", "hyperdiploids" (DNA index up to 1.3), "tetraploids" and "hypertetraploids" (DNA index >2.1) is small, so we can not presently verify if these sub-groups are associated with different survival. Estrogen receptors (ER+_15 fmoles/mg prot.), progesterone receptors (PR+_15 fmoles/mg prot.) and cathepsin D values (Cat D+_30 pmoles/mg prot.) were not significantly related with DNA index. No significant association of SPF with ER (p=0.326), neither with PR (p=0.262) were observed. Tumours with Cat D+_30 pmoles/mg prot. had significantly higher mean values of SPF (p=0.018) and we confirmed the reported association of SPF with tumour grade (p=0.003). SPF values for "diploids" ranged between 3.8% and 16.3% with a mean value of 8.7±2.8(SD). SPF values for "aneuploids" ranged between 2.7% and 41.0% with a mean value of 19.2ñ8.3 (SD). We calculated the tertiles and divided the tumours in three subgroups: low, moderate and high SPF. The high SPF subgroup has a tendency to present a higher risk of recurrence (RR=4.65) and mortality (RR=1.36). In spite of the small size of this series of studied patients, the results of this first analysis reflect already an agreement with other studies. We are working with this perspective and looking forward to find other colleagues, namely members of the Iberian Society of Cytometry, willing to join forces in order to clarify the usefulness of clinical DNA cytometry.