Historical Perspective. Viral Pathogenesis and Natural History of Cervical Neoplasia. Classification Systems for Precursor Diagnosis. Criteria for Grading Squamous Intraepithelial Lesions. Differential Diagnosis of Low Grade Squamous Intraepithelial Lesions. Differential Diagnosis of High Grade Squamous Intraepithelial Lesions. Nondiagnostic Squamous Atypia. Glandular Precursors, Adenocarcinomasand Their Mimics. Diagnosis and Differential Diagnosis of Early Invasive Squamous Cell Carcinoma. Laboratory Management and Clinical Impact