Objective: Our purpose was to develop a mouse model of renal abscess to study the effect of extrauterine infection on preterm delivery. Methods: Escherichia coli or sterile medium was injected into the left kidney of 70 pregnant mice that had completed approximately 75% of gestation. Preterm delivery rates were recorded for various inocula. Kidney specimens were obtained and examined grossly and histologically for abscess formation. Results: Thirty-one of 51 animals (60.8%) infected with 1 × 105–9 × 106 bacteria and none of 19 uninfected animals delivered prematurely (P < .001). Renal abscess was induced in 100% of mice receiving bacterial inoculation but in none receiving sterile medium. Conclusion: Kidney injection provides a reliable method for inducing renal abscess in pregnant mice. Renal abscess induces preterm delivery at a stable rate across a wide range of bacterial inocula. This model of extrauterine infection may be particularly useful in investigations of infection-induced preterm delivery.