The establishment of additional powerful prognostic markers in breast cancer patients is of unquestionable importance given that breast cancer is characterized by morphologic, biologic and genetic heterogeneity. In the present study we analyzed 8 primary invasive breast carcinomas by comparative genomic hybridization (CGH) in order to find and map the DNA copy number changes occurring in these tumors. Furthermore, in order to evaluate the potential prognostic significance, we compared these genetic changes with other histo- and immunopathologic prognostic variables, such as tumor type, tumor grade, lymph node status, estrogen receptors content and c-erbB-2 oncoprotein expression. All the studied cases showed a wide variety of gains and losses of chromosomal regions or arms distributed among 16 chromosomes with an average number of 6.12 aberrations per case. Although several genetic changes appeared to be common, none was unique or consistent in all the studied cases. The most consistent regions of gain were on 1q, 20q and 8q while the most common regions of loss on 3p and 6q. Accumulation of chromosomal changes were more frequently found in high grade ductal breast carcinomas with overexpression of c-erbB-2 oncoprotein in both lymph node-negative and lymph node-positive patients, whose tumors were positive for estrogen receptors. If any of these genetic changes identified by CGH in breast cancer patients carry prognostic information, regardless of stage or other factors predictive of biologic behavior, further investigation is needed.