PURPOSE: Intrauterine device (IUD) is one of the most convenient contraceptive procedures used by women of Asian and African countries. Previous surveys have revealed that 75% of the IUDs recovered from patients suffering from reproductive tract infections (RTIs) were covered with a consortium of microbes. This study was designed to characterize these microbes and recommend remedial measures. METHODS: Quantitative measurement of biofilm formation was assessed by a microtitre plate assay on 86 samples of microorganisms dislodged from IUDs of patients with RTIs. Susceptibility of biofilm to various antimicrobial agents was also quantified. Scanning electron microscopy (SEM) was used to scrutinize the microorganisms adherent to IUDs. RESULTS: The organisms associated with IUDs were predominantly composed of Staphylococcus aureus (16%), Staphylococcus epidermidis (18%), Pseudomonas aeruginosa (5%), Escherichia coli (27%), Neisseria gonorrhoeae (2%), Candida albicans (20%) and Candida dubliniesis (12%). SEM studies indicated that these organisms were organized into biofilms. Studies on the in vitro adherence pattern by crystal violet staining on 96 well microtitre plates revealed that the biofilms were stably established after 60 hours. These biofilms are resistant to an array of antibiotics tested. CONCLUSION: Biofilm formation may be one of the major causes for persistent infection and antibiotic resistance in IUD users.