The recent report of 209 cases of septic spontaneous abortion and 11 maternal deaths in the United States in women using the Dalkon Shield intrauterine device (IUD) raised the question about a possible causal relationship between the IUD and pelvic sepsis. It is essential to determine whether or not this sipsis is unique to the Dalkon Shield or generic to all types of IUDs. Our studies permit the conclusion that the tail of the Dalkon Shield is structurally and functionally different from the tails of the four other IUDs tested. The unique characteristics of the Dalkon tail theoretically could provide a mechanism whereby pathogenic bacteria from the vagina enter the uterine cavity and cause sepsis.