Peyronie's disease (PD) is a localized disorder of the connective tissue of the tunica albuginea (TA) whose etiology has not been elucidated. Although several studies have implicated genetic susceptibility and/or mechanical trauma as triggering events for PD, the underlying molecular mechanisms remain largely unknown. Aquaporin 1 (AQP1) is a water channel protein potentially implicated in connective tissue resistance to mechanical stress, acting primarily by increasing tension within the collagen network. Although it represents a potentially attractive molecular target in PD, to date no studies had ever addressed whether AQP1 is detectable and/or differentially expressed in the TA of these patients. Herein the present study, through immunohistochemical and biochemical approaches, we were able to detect AQP1 expression in the TA of control and PD affected patients. We demonstrated that AQP1-like immunoreactivity and expression are significantly increased in plaques of PD patients Vs controls, implying that AQP1 overexpression might be the consequence of a localized maladaptive response of the connective tissue to repeated mechanical trauma. In summary, these data support the idea that AQP1 might represent a potentially useful biomarker of mechanical injury in the TA and a promising target for the treatment of PD.