"Purpose: To evaluate the clinical features according to co-morbidity in patients with acute hemorrhagic cystitis who visited the emergency room. Materials and Methods: We evaluated 60 patients who visited the emergency room due to acute hemorrhagic cystitis symptoms. We evaluated voiding and storage symptoms, urine analysis, urine culture, and presence of co-morbidities, and analyzed clinical features between group of presence of co-morbidity (group I) and absence of co-morbidity (group II) through review of medical records. Results: The mean age of 60 patients was 55.3±22.3 years (19-84) including 14 male (23.3%) and 46 female (76.7%). The mean age of group I (n=37) and II (n=23) were 62.9±19.8 (22-84) and 43.4 ±17.8 years (19-74), respectively (p=0.102). The most common clinical symptom was dysuria (35.0%) followed by frequency (11.7%) and urgency (3.3%). Pyuria more than 5 WBC/HPF in urine was revealed in 36 patients (60.0%): 22 (59.5%) and 14 (60.8%) in group I and II, respectively (p>0.05). Positive urine culture was found in 25 patients (41.7%): 18 (81.8%) in group I and 7 (18.4%) in group II, respectively (p<0.05), and cultured organisms were E. coli (68.0%), Entrococcus (20.0%), Pseudomonas (4.0%) and Sphingomonas (4.0%). Conclusions: Patients with acute hemorrhagic cystitis were more frequently found in female. The most common symptom was dysuria and more than half of the patient showed positive urine culture. Positive urine culture was more frequently revealed in patients with co-morbidity."