Background: Intrauterine device (IUD) is a convenient, effective and one of a long term contraceptive procedures. However, it may act as a reservoir of reproductive tract infections. Aim of the study: to isolate the microorganisms in the cervix and on the removed IUDs after different times in situ ,examine their association with microbial biofilm formation on  the removed intrauterine devices, and also to detect some common sexually transmitted bacteria. Subjects and Methods: a total of 40 women selected randomly from the Gynecological outpatient clinic of Al-Glaa Teaching Hospital in Cairo were included. Cervical swabs and the removed IUDs were bacteriologically examined. The removed IUDs were analyzed by electron microscope to identify the presence of a microbial biofilm. Real time polymerase chain reaction (PCR) was performed to detect some common sexually transmitted infections (STIs) organisms. Results: The mean age of the studied women was 32.12±6.7 years and the mean duration of IUDs in situ was 2.55±0.87 years . Mixed organisms (E. coli, Enterococcus faecalis, Candida , Staph aureus and others) were detected with no significant differences between the isolated organisms from  the removed IUDs (116 ) and that from cervical swabs (134 )  ; neither nor to the duration of IUDs in situ (p>0.05). Chlamydiae trachomatis(55%,70%),Neisseria gonorrheae(30% ,30%) and Mycoplasma (7.5%,0.0%), were detected STIs organisms by PCR from IUDs and swabs respectively with no statistical significant differences (p> 0.05). Thick biofilm of multiple microorganisms was detected on the surfaces of the removed IUDS. Conclusion:The insignificant association between microorganisms that were isolated from the cervix, removed IUDs and biofilms may indicate the pre-existence of those organisms before and spread by IUDs insertion . IUD  may act as a reservoir for resistant microorganisms. The presence of some asymptomatic sexually transmitted infections (STIs), may point to ,that women may act as STIs transmitters. Prior to and throughout IUDs use, appropriate management of reproductive tract infections is vital. IUDs related prospective studies are also recommended.