The efficacy of condoms in preventing contamination of the transvaginal ultrasound transducer head and possible transmission of blood-borne pathogens is unknown. Our objective was to determine the rate of contamination of the transvaginal ultrasound probe after use in the emergency department. After indicated transvaginal ultrasound scans, the latex condom was removed and the transducer head was inspected for contamination. The presence of vaginal bleeding and the duration of the ultrasound scan were noted. Ten milliliters of hydrogen peroxide (H2O2) was placed in the condom. Bubbling, which occurs in the presence of blood or cervicovaginal secretions, was considered a positive test. Exposure of a clean condom or coupling gel to H2O2 did not cause bubbling. Two-tailed Fisher's Exact and Student's t tests were used for statistical analysis. Of 173 cases, 8 (5%) had a positive H2O2 test for contamination. In only 3 of these 8 cases was gross contamination seen. Latex condoms are ineffective in preventing contamination of the transvaginal ultrasound transducer head. Visual inspection of the transducer head often fails to identify the presence of blood or body fluids. This suggests that additional measures should be taken to prevent transmission of blood-borne pathogens.