Objective: The FDA recently approved adjunctive HPV testing from the vial of PreservCyt(R) Solution used for the ThinPrep(R) Pap Test. We have now evaluated the potential for routine chlamydia testing from cellular material collected for primary Pap testing using the fluid-based ThinPrep method.Methods: Cervical scrapings were collected for a conventional Pap smear and residual material adhering to the sampling implement after slide preparation was suspended in PreservCyt Solution. Chlamydia testing was performed on this residual material using two methods. 1) A slide was prepared using the ThinPrep 2000 System for a determination by direct fluorescence. 2) One mL of the cell suspension was removed and processed for determination by an amplified DNA probe technique. A separate conventional endocervical swab sampling from the same patient was used for testing by an independent direct DNA probe technique (reference method). One hundred specimens were selected and intentionally biased, 19 positive and 81 negative based on the independent swab results, for comparison to the slide and amplified DNA probe methods.Results: The slide-based method gave a sensitivity of 84% (16/19) and a specificity of 100% (81/81). Of 3 discrepant specimens, 2 tested positive by the amplified probe method, while all 3 remained negative by repeat DFA. The amplified probe method gave a sensitivity of 95% (18/19) and a specificity of 99% (80/81) after analysis of discrepant samples by repeat testing.Conclusions: Feasibility has been demonstrated for accurate and effective routine testing for chlamydia with either DFA or DNA probe methods, from a single, fluid-based sample already approved for primary Pap screening.