The most important complication attributed to the use of intrauterine device (IUD) is pelvic inflammatory disease (PID), often associated with Neisseria or Chlamydia infection. Consequently, the IUD should not be inserted in women at risk of infection or with symptoms of endocervicitis. To evaluate the effectiveness of such a policy, a systematic investigation of Chlamydia and Neisseria was carried out among 407 contraceptive acceptors. Twenty-seven cases were positive for Chlamydia and none were positive for Neisseria. There were no statistical differences in the proportion of women with and without Chlamydia who had vulvovaginal or cervical signs or symptoms, although twice as many women had pain at pelvic exam in the Chlamydia-infected group. In 29 women in whom infection was clinically suspected, two were found to be infected with Chlamydia. IUD were not inserted in women suspected of having infection, but 19 of 327 IUD acceptors were subsequently found to have a positive Chlamydia test result. Two women returned with symptoms of PID and 17 were asymptomatic, but all were treated. PID was not suspected in any other subject. These results reinforce the need for careful selection of IUD acceptors and for thorough counseling for symptoms of PID and the need for immediate consultation.