We measured plasma concentrations of TGF-beta 1 in patients with obstructive ureteral calculi and compared them with the plasma concentrations of healthy volunteers. The present study was a prospective study containing a homogenous group of patients with unilateral ureteral obstruction (UUO). The study consisted of patients with ureteral stones less than 7 mm in diameter that caused mild to moderate obstruction. All patients were referred by the emergency department of our hospital and examined between April 2003 and April 2004. The presence and characteristics of both stone and obstruction were determined by plain abdominal x-ray and gray-scale ultrasonography (US). Blood samples were collected from both patients and control individuals on admission and 1 week after conservative follow-up. The plasma TGF-beta 1 concentration was determined using a quantitative sandwich enzyme immunoassay specific for TGF-beta 1. There were 35 patients with 20 women and 15 men (average age 26.8 +/- 5.9 years), and 15 volunteers in the control group, with nine women and six men (average age 24.2 +/- 4.5 years). Average stone size was 5.6 mm +/- 1.2 mm (range 3.5-7) for the patient group. US showed the presence of mild hydronephrosis in 24 and moderate hydronephrosis in 11 patients. Plasma concentrations of TGF-beta 1 in patients with ureteral obstruction (1,117 +/- 5.8 ng/ml, range 36-2,442 ng/ml) were significantly higher than those in the healthy control group (32 +/- 4 ng/ml) on admission (P < 0.001). There was a significant increase in TGF-beta 1 plasma concentrations in the patient group (33,525 +/- 6.8 ng/ml, range 1,107-73,288 ng/ml) after 1 week follow-up (P < 0.001). Ureteral obstruction increases plasma TGF-beta 1 concentrations in patients with ureteral stones as in UUO models in animal studies. A concomitant treatment with an anti-fibrotic agent may reduce the incidence of renal injury during obstruction.