['Tumour-infiltrating forkhead box P3 (FoxP3+ ) regulatory T cells (T(regs) ) have stronger prognostic significance than cytotoxic CD8+ T cells in colorectal cancer (CRC). Because there is evidence that some tumour-infiltrating CD8+ T cells may be inactive, the present study aimed to investigate the prognostic significance of Granzyme B, one of the major effector molecules of T cells.', 'A tissue microarray containing 963 CRCs was stained immunohistochemically for Granzyme B and the level of expression quantified by digital image analysis. Granzyme B expression was higher in tumours with microsatellite instability (P\u2003<\u20030.0001), a dense lymphocytic infiltrate (P\u2003<\u20030.0001) and location in the proximal colon (P\u2003=\u20030.009), but lower in tumours with vascular invasion (P\u2003=\u20030.007), perineural invasion (P\u2003=0.041) and positive nodal status (P\u2003<\u20030.001). Elevated expression of Granzyme B was associated with improved survival on univariate analysis (hazard ratio\u2003=\u20030.65; 95% confidence interval 0.51-0.84; P\u2003=\u20030.001), but not in a multivariate model that included stage, vascular invasion and FoxP3+ T(reg) cell density.'] Is low expression of Granzyme B in colorectal cancer associated with signs of early metastastic invasion?