Investigators in DCEG and the Division of Cancer Prevention conducted a study of the clinical management of minor cervical cytologic abnormalities. The major hypothesis tested was whether HPV testing could be used reliably and accurately to triage the common cytologic diagnoses of ASCUS (atypical squamous cells of undetermined significance) and LSIL (low-grade squamous intra-epithelial lesions), which represent the bulk of cervical abnormalities seen on Pap smears. This clinical trial of management alternatives consisted of three arms: immediate colposcopic referral of all patients; triage using HPV testing as an adjunct to cytology; and conservative management with repeat Pap smears. All participants were followed every six months for two years. Over 5,000 women were randomized during enrollment that ended in December, 1998. The data showed that HPV DNA testing is a viable strategy for clarifying ASCUS cytology. However, HPV DNA prevalence in cases of LSIL proved too uniformly high to permit use of HPV DNA testing for triage. Residual specimens from ALTS are being used to validate new HPV tests, and to explore natural history questions.