The prevailing approach to Papanicolaou (Pap) and endocervical Gen-Probe(R) screening is to use an unlubricated vaginal speculum because of concerns that gel lubricant interferes with Pap smear adequacy and cervical microbiology. This study tests the hypothesis that lubrication of metal specula with a bacteriostatic gel does not increase unsatisfactory cervical cytology or decrease detection rates of endocervical Chlamydia trachomatis or Neisseria gonorrhoeae. At a publicly funded family planning clinic site, each of eight consecutive months was randomly designated by computer as an exclusively gel-lubricated or water-moistened specula use month. The assigned vaginal speculum intervention was used on all patients receiving a Pap smear and/or combination DNA probe assay for endocervical C. trachomatis and N. gonorrhoeae. From July 2003 through February 2004, 3460 Pap smears and 5535 combination probe assays for C. trachomatis and N. gonorrhoeae were collected from 6538 patients. During the 4 months of gel lubricant use, the rate of unsatisfactory cytology was 1.1% compared to 1.5% during the 4 months of water lubrication [odds ratio (OR) 0.74; 95% confidence interval (CI) 0.41-1.35]. During the 4 months of gel lubricant use, the detection rate for endocervical C. trachomatis was 1.5% compared to 1.5% (OR 1.05; 95% CI 0.67-1.62) in water lubricant months. The study population N. gonorrhoeae infection rate was too low to statistically analyze. The use of a small amount of gel lubricant on metal vaginal specula did not increase unsatisfactory cytology or decrease endocervical C. trachomatis detection rates when compared to water lubricant.