A case-control study examining the risk for post-abortal endometritis in patients undergoing an immediate intrauterine device insertion after suction curettage for first trimester elective abortion was completed. The relative risk for endometritis in patients receiving the Dalkon Shield and Lippes Loop respectively was 0.56 and 0.33 when endometritis cases were matched with suitable controls. The significance of this finding and possible sources of bias are discussed.