Members of the transforming growth factor beta (TGF-beta family, in particular TGF-beta 1, are some of the most potent inhibitory growth factors in a variety of cell types. Resistance to TGF-beta 1-induced growth inhibition is frequently observed in colorectal carcinomas and is associated with tumour progression. Perturbations of TGF-beta 1 expression and function, therefore, may contribute to the loss of some constraints on tumour cell growth. In this study we have examined the expression of TGF-beta 1 and its precursor latency-associated peptide (LAP)-TGF-beta in human colorectal tumours using immunohistochemical techniques. In 86% of the tumours the LAP-TGF-beta complex was present in both the stromal and epithelial cells, whereas the mature TGF-beta 1 peptide was expressed in the glandular epithelium of 58.3% of these tumours. Intense staining for TGF-beta 1 was positively associated with advanced Dukes' stage. Furthermore, there was a significant correlation between the presence of TGF-beta 1 in the tumours and a shorter post-operative survival. This was most significant in a subgroup of patients who had received only a palliative operation. These results suggest that TGF-beta 1 expression may be useful as an independent prognostic indicator for a subgroup of patients who have a particularly poor prognosis.