To assess the AutoPap 300 QC System's sensitivity to cases of high grade squamous intraepithelial cervical lesion and invasive cervical cancer, a comparison of outcome was made in cases that had surgical biopsy confirmation. The sensitivity of the device to biopsy-confirmed diagnostic categories at the level of high grade squamous intraepithelial lesion (HSIL) and greater was calculated. At two of six clinical trial sites, biopsy data were available and were compared to device scores indicating whether a case would or would not be selected for 10% or 20% quality control rescreening. In 86 biopsy-positive cases that had a cytologic diagnosis of HSIL or greater, the device indicated inclusion in the 10% or 20% review fraction for 66 slides (77%) and 74 (86%), respectively. This figure indicated an approximately eightfold improvement in the ability of the device to include such cases for quality control rescreening when compared to a 10% random case selection process. These data showed that the sensitivity of the AutoPap in identifying cases of HSIL and greater was similar to that previously calculated for these diagnostic categories in clinical trials, when calculated on the basis of an alternate or "higher" standard of tissue confirmation.