We investigated delayed-type hypersensitivity to human papillomavirus (HPV) in women with cervical dysplasia or cancer. Women were challenged by skin tests with synthetic HPV-16 E7 oncoprotein peptides. 11 women were regressors (cleared disease without treatment) and 37 were progressors (required surgery). Antibodies to early antigens (markers for progression) were detectable in a higher proportion of cancer patients than all other patients, particularly progressors with cervical intraepithelial neoplasia (CIN). By contrast, cellular immunity to HPV-16 E7, measured by skin test, was significantly (p=0.0001) associated with clinical and cytological resolution of HPV-induced CIN, indicating that E7-specific T-helper cells have a role in control of HPV.