Objectives. To examine the distribution of periurethral collagen by three-dimensional ultrasonography (3D US) and to incorporate this technology into a practical treatment decision tree for women with stress urinary incontinence desiring collagen injection. Methods. Forty-six women who received periurethral collagen injection were assessed with 3D US to document the position and volume of collagen around the urethra. Patients with a good clinical response were observed with serial 3D US scans. Women with no persistent improvement who showed a low volume or asymmetric distribution of collagen were offered repeat injections. When the patient had no improvement despite symmetric or circumferential distribution of collagen with good volume retention, another anti-incontinence treatment was recommended. Group 1 was composed of women who had a good clinical outcome and group 2 of those who did not. A statistical comparison between the two outcome groups was done to determine whether any particular distribution pattern was associated with an increased likelihood of clinical success. Results. Of the 46 patients, 21 (46%) were satisfied with their continence after their last periurethral collagen injection, with a median follow-up of 14.0 months (range 2 months to 4.25 years). A significantly greater proportion of patients in group 1 had circumferentially distributed collagen on 3D US compared with those in group 2 (62% versus 20%, P = 0.006). Conclusions. Circumferential distribution of collagen around the urethra is associated with a higher likelihood of clinical success. The assessment of periurethral collagen by 3D US provides an affordable, noninvasive, objective outcome measure that may aid in treatment planning. © 2003 Elsevier Inc.