Objective To explore the establishment of a rat model of interstitial cystitis based on intraperitoneal injection of cyclophosphamide. Methods Saline or gradient concentrations of cyclophosphamide were intraperitoneally injected in rats to establish an animal model of interstitial cystitis. The grade of bladder inflammation was then estimated at the histological and molecular levels based on hematoxylin-eosin staining and real-time polymerase chain reaction. The rats’ pain sensation was tested by both behavior recording and Von Frey examination. Mortality during the study was also recorded. Results The bladder inflammatory indices and pain sensitivity of the rats in the 150-, 200-, 250-, and 300- mg cyclophosphamide groups were significantly higher than those of the control rats. Urodynamic examination revealed impaired contraction capacity of the rats’bladders in the 250- and 300-mg cyclophosphamide groups. Rats in the 100-mg cyclophosphamide group showed observable inflammatory changes in their bladders without a significant increase in sensitivity to spontaneous visceral pain or somatic nociception. The rats in the 50-mg cyclophosphamide group showed no alteration of bladder inflammatory indices or pain sensitivity. Some rats died within 48 hours after cyclophosphamide injection in the 200-, 250-, and 300-mg groups. Conclusions Intraperitoneal injection of cyclophosphamide is a feasible and reliable method for the establishment of a rat model of interstitial cystitis, showing the two critical features of this disease: bladder inflammation and pain sensation. Based on our data, we recommend 150 mg / kg as a suitable dose for the establishment of a rat model of interstitial cystitis.