Objective. The liquid-based cytology Pap test was adopted as the exclusive collection method for cervical cytology in military treatment facilities within the National Capital Area in 2001. We sought to determine the impact of converting from conventional to liquid-based cervical cytology. Methods. A retrospective population-based study was performed to analyze the cervical cytology results from the National Capital Area for fiscal years 1999, 2000, 2002, and 2003. Using a computer database, the results of 78,738 conventional and 76,675 liquidbased cervico-vaginal cytology examinations were reviewed. All cytology samples during the study period were collected with the same collection device and were processed in a single laboratory. Results. An increase of 116%(P < 0.005) in the mean rate of LSIL detection and a 38%(P < 0.005) increase in HSIL detection were noted with conversion to liquid-based cytology. A 65%(P < 0.005) decrease in the mean rate of atypical glandular cell detection was also observed. However, a mean increase of 46%(P < 0.005) per year was noted in the unsatisfactory rate with conversion to liquid-based cytology. The incidence of cervical carcinoma did not change during the study period. Conclusions. Consistent with previous reports, conversion from conventional to liquid-based Pap testing in this population resulted in a significant increase in the detection rates of both LSIL and HSIL. Contrary to earlier studies, we noted an almost 50%increase in the number of unsatisfactory samples after conversion. Further studies are warranted to determine the potential etiology of these findings to include the role of collection devices. Objective-The liquid-based cytology Pap test was adopted as the exclusive collection method for cervical cytology in military treatment facilities within the National Capital Area in 2001. We sought to determine the impact of converting from conventional to liquid-based cervical cytology. Methods. A retrospective population-based study was performed to analyze the cervical cytology results from the National Capital Area for fiscal years 1999, 2000, 2002, and 2003. Using a computer database, the results of 78,738 conventional and 76,675 liquidbased cervicalico-vaginal cytology examinations were All cytology samples during the study period were collected with the same collection device and were processed in a single laboratory. Results. An increase of 116% (P <0.005) in the mean rate of LSIL detection and a 38% (P < 0.005) increase in HSIL detection were noted with conversion to liquid-based cytology. A 65% (P <0.005) decrease in the mean rate of atypical glandular cell detection w As also observed. However, a mean increase of 46% (P <0.005) per year was noted in the unsatisfactory rate with conversion to liquid-based cytology. The incidence of cervical carcinoma did not change during the study period. Conclusions. Consistent with previous reports, conversion from conventional to liquid-based Pap testing in this population resulted in a significant increase in the detection rates of both LSIL and HSIL. Contrary to earlier studies, we noted an almost 50% increase in the number of unsatisfactory samples after conversion Further studies are warranted to determine the potential etiology of these findings to include the role of collection devices.