Twenty per cent of cervical intraepithelial neoplasias-III (CIN-III) progress to invasive cancer. Human papillomavirus (HPV) infection alone does not determine progression. GIN-III lesions were collected from 161 women. Each tissue was microdissected into a maximum of 32 contiguous units and assayed at multiple microsatellite loci on chromosome 11q, a region frequently deleted in invasive cervical and other cancers. Eight of 108 informative cases (7%) had 11q23.3-q25 deletions; focally intra-lesional in six tone with focal loss of alternate alleles), and pan-lesional in two cases. Hence, 11q deletion can occur early in cervical neoplasia, and possibly predisposes to invasion.