When a Pap test is referred for pathologist review, it is accompanied by the cytotechnologist's provisional interpretation. Discordant interpretations between pathologists and cytotechnologists are sometimes noted. The objective is to correlate HPV detection rate with both estimated false-negative fraction (EFNF) and ASC to SIL ratio among discordant ASC cases. ThinPrep Pap tests in which the cytotechnologists' provisional interpretations were up- or down-graded by pathologists to ASC were retrieved between January and December 2006. HPV DNA testing was performed using hybrid capture technique. EFNFs and ASC to SIL ratio were estimated for cytotechnologists and pathologists, respectively. Overall, the EFNF ratio was 3.4% and the high-risk HPV DNA detection rates in cases that were "over-" or "under-" interpreted by technologists were 0.71 and 0.40, respectively. The overall ASC to SIL ratio was 1.41 and the high-risk HPV DNA detection rates in cases that were upgraded or downgraded to ASC were 0.40 and 0.71, respectively. In conclusion, our ASC to SIL ratios and EFNF were within acceptable range. We did not observe any association between ASC to SIL ratio and HPV detection rate in cases that were upgraded or downgraded to ASC by pathologists or between EFNF ratio and HPV detection rate in cases that were "over-interpreted" (or "under-interpreted") by cytotechnologists. The HPV detection rates for ASC cases that were originally "over-interpreted" by cytotechnologists were comparable to the HPV detection rates for LSIL, whereas those that were underinterpreted were comparable to the HPV detection rate for ASC. © 2009 Wiley-Liss, Inc.