Chlamydia trachomatis is the most common sexually transmitted organisms. Endocervicitis is the most common site of infection which may be asymptomatic and can progress into upper genital tract to produce serious complications.The aim of the present work is to evaluate the role of Chlamydia trachomatis infection as a cause of first trimester abortion.The result of the study proved that using anti-chlamydial antibody IgG with the high sensitive and accurate polymerase chain reaction technique to detect the chlamydial DNA indicated that the Chlamydia trachomatis infection has a role in causing first trimester abortion especially in recurrent abortion.