Objective: In this research, we studied the TGF-β1 effects on connexin-43 expression in cultured human bladder smooth muscle cells. Methods: Human bladder smooth muscle cells primary cultures, with bladder tissue obtained from patients undergoing cystectomy, were intervened by recombinant human TGF-β1. Connexin-43 expression in human bladder smooth muscle cells was then examined by West blotting and immunocytochemistry. Results: Stimulation with TGF-β1 led to significant reduction of cormexin-43 immunoreactivity and coupling (P<0.0001). Connexin-43 protein expression was significantly downregnlated (P<0.05). Simultaneously, low phosphorylation species of connexin-43 were particularly affected. Conclusion: Our experiments demonstrated a significant downregulation of connexin-43 by TGF-β1 in cultured human bladder smooth muscle cells. These findings support the view that TGF-β1 is involved in the pathophysiology of urinary bladder dysfunction.