Objective: Previous studies have demonstrated diagnostic discrepancies for the detection of high-grade cervical intraepithelial neoplasia (CIN 2/3) from previously confirmed cytological high-grade squamous intraepithelial lesions (HSILs). The goal of this study is to investigate the possible factors which may be responsible for this diagnostic discrepancy. Study Design: The study included all the cytological specimens diagnosed with a HSIL by the Papanicolaou (Pap) test at Temple University Hospital (2000-2010) as well as timely follow-up cervical biopsies. The biopsy tissue types and diagnoses were subsequently categorized and analyzed. Results: Of the total 842 Pap tests with HSIL diagnosis, 96 cases (11.4%) showed non-CIN 2/3 in follow-up cervical biopsies. Among those cases, the most common biopsy diagnoses were cervicitis (27.9%) and CIN 1 (25%). Endocervical curettage (ECC) samples showed a high percentage of inadequacy for diagnosis (43.7%). Thirty-seven cases had subsequent follow-up biopsy, and CIN 2/3 was found in 15 cases. However, none of the CIN 2/3 cases was detected by ECC sampling. Conclusions: Our study indicated that the discrepant correlation between HSIL and CIN 2/3 was most likely due to tissue sampling issues during colposcopic examination. The diagnostic value of ECC remains poor for the detection and grading of cervical intraepithelial dysplasia.