Nm23 is a putative metastasis suppressor gene and alterations in this gene have been reported in colorectal carcinomas suggestive of a role for nm23 in the dissemination of these tumours. In this study we used an affinity purified polyclonal antibody, ab-11, on formalin-fixed, paraffin-embedded sections of colorectal carcinomas from 46 patients in a three-stage avidin-biotin complex immunoperoxidase technique. Follow-up of these patients was until time of death or for 5 years, with a mean time of 31.2 months. Two observers scored the staining results from 1 to 3 according to the proportion of tumour cells positive. The association of nm23 staining with survival, sex, age, vascular invasion, and Dukes' stage was determined using Cox's regression model. The association of death from colorectal cancer and nm23 status reached marginal significance in this study (P = 0.0417). Moreover, there is some suggestion of a protective effect from nm23 as the relative risk of dying from colorectal cancer for each increment of nm23 positivity is 0.573 (95 per cent confidence limits 0.34-0.98).