Transforming growth factors beta (TGF-beta) constitute a family of polypeptide growth factors that control cell growth, cell differentiation and migration, as well as the formation of the extracellular matrix. Recent analyses revealed the overexpression of TGF-beta1 in human gastric cancers and demonstrated increased cell proliferation in the stomach of patients with gastric cancer and their first-degree relatives. Using human gastric tissues obtained from patients with gastric cancer (n = 19), biopsies from healthy first-degree relatives of gastric cancer patients (n = 18) and healthy individuals (n = 19), we analysed the expression of TGF-beta1 using the reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. Fifteen of 19 patients with gastric cancer expressed TGF-beta1 in the tumour. In 11 of these 15 cases TGF-beta1 mRNA was also detectable in the non-tumourous stomach. Interestingly, all but two individuals with a first-degree relative diagnosed with gastric cancer exhibited TGF-beta1 expression in either the antrum or corpus biopsy or both. In contrast, only one of 19 individuals without a family history of gastric cancer expressed TGF-beta1 in the stomach (P< 0.0001). TGF-beta1 expression is detectable in a large proportion of gastric cancers and in the stomach of healthy first-degree relatives of gastric cancer patients. Since individuals without gastric cancers in their family express TGF-beta1 only in one of 19 cases, the induction of TGF-beta1 expression in first-degree relatives of patients with gastric cancer points to the presence of specific molecular alterations in a subgroup of individuals with an increased risk of developing gastric cancer that may precede the development of gastric cancers.