Objective. To evaluate whether preoperative vaginal preparation routines influence postoperative infectious morbidity in vaginal hysterectomy and to analyze risk factors for postoperative infectious morbidity. Design. Retrospective, longitudinal cohort study. Setting. Forty -three hospitals in Sweden, participating in the Swedish National Register for Gynecological Surgery. Population. All 6,496 women who were enrolled in the Register and underwent vaginal or laparoscopically assisted vaginal hysterectomy between 1 January 2000 and 1 February 2008. Methods. Register data were collected prospectively using doctors' forms and patient questionnaires. Information about vaginal preparation routines in the clinics were achieved retrospectively by an e-mail survey. Multiple logistic regression analyses models were used to determine associations and risk factors. Main outcome measures. Infectious morbidity within 6–8 weeks postoperatively. Results. No significant differences were seen in postoperative infectious morbidity in long term between vaginal preparation using saline or chlorhexidine solution or no cleansing. At discharge from hospital, those who had had vaginal cleansing using saline solution had a significantly higher risk of postoperative infections. Risk factors for infectious morbidity were young age, obesity, peroperative injury of the urinary bladder, operative time and duration of hospital stay. Protective were prophylactic antibiotics and concomitant prolapse surgery. Conclusions. Saline solution should not be used for vaginal cleansing due to a higher risk of infectious morbidity in the immediate postoperative period. Infectious morbidity may be reduced further by employing preventive measures such as meticulous surgical technique, preoperative weight reduction in obese women and minimizing time in hospital.