The gadd153 gene belongs to the CCAAT/enhancer binding protein (C/EBP) family of transcription factors. The role of these proteins in the control of proliferation and differentiation have mostly been studied in vitro. The involvement of gadd153 gene expression in human disease, and most particularly in breast cancer, is largely unknown. Since gadd153 gene is normally expressed at very low levels in most cells, we developed a sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) technique that permits the detection of low amounts of RNA. In these conditions, 24 breast tumors and 14 corresponding normal samples were analysed, and levels of expression between tumor and normal tissues were compared. Statistical analysis indicated a significant induction of gadd153 gene expression in tumor samples in comparison to normal ones (p<0. 01). Thus, overexpression of gadd153 may inhibit the cellular differentiation process and facilitate breast tumorigenesis. Further studies are needed with larger number of cases to determine the specific prognostic role of gadd153 in breast cancer.