The effect of large uterine fibroids on urinary bladder function and symptoms. Fourteen patients with large uterine fibroids and urinary symptoms were treated with monthly injections of [D-Trp6]-luteinizing hormone-releasing hormone microcapsules. The average uterine size before treatment was 728 ml; it dropped to 323 ml (a drop of 55%) after treatment. Urinary symptoms of diurnal frequency disappeared in 11 of 12 patients (p less than 0.005) after the reduction of uterine size. Urgency decreased in 11 of 13 (p less than 0.005) and nocturia in eight of 10 (p less than 0.02). No differences were found before and after treatment in the symptoms of urge incontinence and stress incontinence in the cystometric and urethral pressure profile measurements. Urinary symptoms of frequency, urgency, and nocturia may be caused by the direct pressure exerted on the bladder by the enlarged uterus. Symptoms of urge incontinence and stress incontinence deserve a more specific treatment as they are not related to uterine size. 