Choline kinase (ChoK) and its product, phosphocholine (PCho), have been implicated in human carcinogenesis. Inhibition of this enzyme has been shown to be an efficient antitumor strategy in vivo. The aim of this study was to assess the relationship between the regulation of ChoK and clinical features in patients with breast cancer. To that end, normal and tumoral tissues from 53 patients with breast carcinomas were analysed for ChoK activity and expression, and compared to some clinical parameters. We report a relevant increase in ChoK activity in 38.5% of the tumoral tissues analysed when compared to the normal levels in healthy tissues. Furthermore, some clinical features were found significant versus ChoK status. First, an association of choline enzymatic activity with histological tumor grade was observed (P<0.001). In addition, increased ChoK activity was also associated with ER-negative breast carcinomas (P=0.037). A significant association between ChoK overexpression and both high histologic tumor grade (P=0.017) and ER-negative tumors (P=0.003) was found. Finally, ChoK overexpression was found in 17% of the samples and all corresponded with those that display the highest increase in ChoK activity (P<0.001). Here we provide evidence that ChoK may be related to the development of human breast cancer, suggesting that this finding may constitute the basis for the development of a novel antitumoral strategy for these patients.