Among women applying for termination of pregnancy, 5-17% are infected with Chlamydia trachomatis. The prevalence is higher among women under 20 years of age (12-30%), in nulliparae and when Neisseria gonorrhoeae are found simultaneously. If women applying for termination of pregnancy with Chlamydia infection are not treated, 10-60% will develop pelvic infection after abortion. Salpingitis caused by Chlamydia runs a milder clinical course than salpingitis caused by gonococci or other etiology but salpingitis due to Chlamydia is regarded as one of the most important causes of tubal infertility and extrauterine pregnancy. The symptoms may be discharge and dysuria or objective findings such as cervicitis and pathological findings in wet smears of the cervical secretion. The majority of women applying for termination of pregnancy with Chlamydia infection have no symptoms. Only few investigations have analysed Chlamydia infection in connection with sexual behaviour and association between Chlamydia infection and the number of sexual partners has been demonstrated. Direct immune fluorescent microscopic examination or enzyme immune examination of material from the cervix and urethra may be employed in women applying for termination of pregnancy on account of the rapid results. Tetracyclines and erythromycin may be employed for treatment of demonstrated Chlamydia infection. Completion of treatment prior to abortion is probably not necessary. The sexual partners should be treated.