The key to successful management of the rudimentary uterine horn is early detection. This review of the literature seeks to illustrate important aspects of diagnosis and management of this anomaly. An English language MEDLINE search from 1966 to 2003 was performed, using the search terms "rudimentary uterine horn," "accessory horn," "uterus bicornis unicollis," "hematometra," "unicornuate or bicornuate uterus," and "mullerian anomaly." References from previously published sources were also obtained. One hundred thirty letters, case reports, case series, and review articles featuring rudimentary uterine horn were found. Reports before 1966 were excluded because outcomes before the advent of modern diagnostic techniques were not relevant to this study. Three hundred sixty-six rudimentary horn presentations (210 gynecologic and 156 obstetric) were found. Noncommunicating horns accounted for 92% of cases (95% confidence interval [CI] 88-95%, P < .001), and renal anomaly was found in 36% (95% CI 29-44%). Contrary to the American Fertility Society classification of uterine anomalies, rudimentary horns may occur without a corresponding unicornuate uterus. The mean age of presentation was similar for gynecologic and obstetric presentations (23 and 26 years, 95% CIs 21.2-24.6 and 124.9-27.3 years, respectively). Presentation in the third decade of life or later occurred in 78% of patients (95% CI 70-84%, P < .001). Sensitivity of ultrasound examination for diagnosis was 26% (95% CI 18-36%). Diagnosis before clinical symptoms occurred in 14% (95% CI 7-23%). Many functional noncommunicating horns present during or after the third decade of life with acute obstetric uterine rupture. Surgical removal before pregnancy is recommended. Rates of prerupture diagnosis remain disappointingly low.