Spermicides containing nonoxynol-9 (N-9) may increase HIV transmission. In women, intravaginal N-9 is found in the uterus shortly after its insertion. Exposure of the female upper reproductive tract to N-9 may alter epithelial integrity, thereby increasing HIV transmission risk. Our goal was to characterize the histological effects of N-9 on uterine epithelium in an animal model. Female mice were exposed to intravaginal or intrauterine Advantage-S (N-9), Replens, K-Y(R) jelly or water. After various exposure times, mice were sacrificed and stained uterine tissue sections were analyzed by a pathologist blinded to treatment.Intravaginal and intrauterine N-9 administration resulted in disruption of uterine epithelium compared to Replens, K-Y jelly or water. N-9 caused rapid (within 10 min), focal, uterine epithelial sloughing and complete epithelial loss within 24 h. Epithelial regeneration began 48 h after exposure N-9 and was completely restored within 72 h; the new epithelial layer, however, was composed of cuboidal cells instead of normally present columnar cells. In addition, hemorrhage and necrosis were present are all time points examined. Our results demonstrate for the first time that N-9 has a deleterious effect on uterine epithelium. Although these results were observed in a mouse model, similar disruption of the upper reproductive tract epithelium in women by N-9 may facilitate HIV infection and serve as an unrecognized portal of human HIV transmission.