Methylation of arginine residues has been implicated in many cellular activities like mRNA splicing, transcription regulation, signal transduction and protein-protein interactions. Protein arginine methyltransferases are the enzymes responsible for this modification in living cells. The most commonly used methyltransferase in man is protein arginine methyltransferase 1 (PRMT1). Since methylation processes appear to interfere in the emergence of several diseases, including cancer, we investigated the localisation of the protein in cancer tissue and, for the first time, the relation that possibly exists between the expression of PRMT1 gene and breast cancer progression. We used tumour specimens from 62 breast cancer patients and semi-quantitative RT-PCR to determine the expression of PRMT1 gene and was found to be associated with patient's age (p = 0.002), menopausal status (p = 0.006), tumour grade (p = 0.03), and progesterone receptor status (p = 0.001). Survival curves revealed that PRMT1-v1 status-low expression relates to longer disease-free survival (DFS; p = 0.036). To the contrary, PRMT1-v2 status is not associated neither with the clinical or pathological parameters nor with DFS (p = 0.31). PRMT1-v3 was not statistically significantly expressed in breast cancer tissue. Selected cancer and normal breast samples were stained for PRMT1. In both normal and cancerous breast tissues, staining was in the cytoplasm and only in rare cases the cell nucleus appeared stained. Present results show a potential use for this gene as a marker of unfavourable prognosis for breast cancer patients.