The TSG101 gene, identified through insertional mutagenesis, is localized in a region that exhibits LOH in human cancers, suggesting that TSG101 might be a tumor suppressor gene. Numerous studies have then shown the presence of abnormal transcripts in various tumors which appear to result from aberrant splicing of the gene, rather than from intragenic deletions. Moreover, many studies demonstrated that these aberrantly spliced transcripts were not found in matched normal tissues. We have analysed TSG101 transcripts in 85 breast cancer samples and found that abnormal splicing of the gene is tightly correlated with tumor grade and p53 mutation. In addition, stress induced the appearance of these abnormal transcripts in primary lymphocytes. Hence, TSG101 splicing defects, while unrelated to the oncogenic process per se, could reflect the cellular environment of the tumor cells. The proposed role of stress and hypoxia to select p53 mutant cells could account for the tight association with p53 status.