There are very few studies on the final triggers of apoptosis, the caspases, in breast cancer. Caspase-3 expression was studied by means of reverse transcript polymerase chain reaction (RT-PCR) in a series of 108 previously untreated patients with breast cancer. Expression levels were correlated with those obtained using the same technique of the apoptosis-associated X-chromosome genes RBMX, RBM3, RBM10 small and RBM10 large variant; Bcl-2 and Bax; the angiogenesis-associated genes VEGF and CD105 (endoglin); hMAM and Nup88. The correlation with the expression of hormone receptors, c-erb-B2, mutant p53 and Ki-67, all measured by means of immunohistochemistry, was also studied, as well as that with standard clinical parameters such as histological type, tumor size, axillary metastasis and DNA-ploidy. The only statistically significant correlations observed between caspase-3 mRNA expression and the parameters tested were a direct one with both the Bax (p=0.007) and the small variant of the X-chromosome RBM10 gene (p=0.018), and an inverse one with the angiogenesis-associated CD105 (endoglin) gene (p=0.044). These results indicate that very few genes are involved in the last steps of the apoptotic cascade in breast cancer, among them one of the X-chromosome RBM family. They also support the relatively unexplored link between apoptosis and angiogenesis.