BACKGROUND The aetiology of inguinal hernia includes changes in collagen turnover and metalloproteinase (MMP) expression, and direct hernia has been linked to increased MMP-2 expression. Since transforming growth factor beta1 (TGFbeta1) plays a role in tissue remodelling, this growth factor could directly affect metalloproteinase secretion and thus the proteolytic activity of these enzymes. We hypothesized that TGFbeta1 expression could also be altered in direct inguinal hernias. METHODS Tissue specimens were obtained from the transversalis fascia (TF) of organ donors (controls; n = 10) and patients with inguinal hernia (indirect; n = 20/direct; n = 20), who were also divided into two groups according to age (20-40/41-60 years). Tissue sections were immunohistochemically labelled using anti-LAP TGFbeta1 (latent form) and anti-TGFbeta1 (active form) antibodies, and fragments of tissue were subjected to Western blot analysis. RESULTS No significant differences in LAP-TGFbeta1 expression were detected between specimens from control and hernia patients. However, significantly higher levels of active TGFbeta1 were detected in the TF of patients with direct hernia (P < 0.05). Age affected the expression of the growth factor in its active form, and significant differences emerged between direct hernias and controls/indirect hernias only in the younger age groups. CONCLUSIONS Our findings indicate overexpression of the active form of TGFbeta1 in the TF of young patients with direct hernia. This overexpression reflects an attempt to counterbalance the enhanced matrix degradation process observed in these patients, identifying a subset of patients requiring the use of a prosthetic material for primary hernia repair.