Capecitabine (Xeloda®) is a tumour-selective fluoropyrimidine carbamate designed to mimic continuous infusion 5-FU and to generate 5-FU preferentially in tumour tissue by exploiting the higher concentrations of thymidine phosphorylase (TP) found in malignant cells compared with normal cells (Miwa et al, 1998). The gene discussed is TYMP; the disease is neoplasm.