Backgrount Cervical cytology designated as atypical squamous cells of undetermined significance (ASCUS) requires either colposcopy or an increased frequency of Pap testing, depending on the clinician's interpretation of patient risk. Recent data has suggested the ability to triage patients with ASCUS based on descriptive qualifiers to the cytology report (“reactive or inflammatory change” versus “dysplasia or human papilloma virus (HPV) change”). This study was undenaken to test whether cytology showing ASCUS favor reactive or inflammatory change would be associated with less histologically confirmed dysplasia than cytology showing ASCUS favor HPV or dysplasia among adolescents in an urban referral clinic. Methods Forty-eight adolescent patients (age 13 through 19) referred with ASCUS on Pap smear over a 24 month period underwent colposcopy and tissue sampling when indicated by colposcopic findings. Cytology had been uniformly evaluated through Boston Medical Center cytopathology lab. Descriptive qualifiers of ASCUS were present for all patients and subjects with “favor reactive or inflammation” (Group A) were compared to those with “favor HPV or dysplasia” (Group B) for presence of dysplasia and recurrent abnormal Pap smears within a year among those undergoing follow-up without treatment. These patients were screened for pregnancy and had negative cervical cultures for gonorrhea and chlamydia in the previous 3 months. Patients with mild dysplasia (first diagnosis) were counselled on the imponance of follow-up and given the option of close follow-up or immediate therapy; all moderate and severe dysplasias were treated with laser or excisional therapy. Histologic specimens were processed al the Boston Medical Center pathology deparment. Data were analyzed using Epi Info 6 statistical softaware (CDC, Atlanta, GA). Relative risks were calculated at 95% confidence intervals. Results There were 18 palients with ASCUS favor reactive (17) or inflammation (1). There were 30 patients with ASCUS favor HPV (15) or favor dysplasia (15). Six in group A had normal colposcopies and 9 in group B group had normal colposcopies. (RR=1.05; CI 0.70–1.57) Colposcopically directed biopsies revealed mild dysplasia in 2 group A patients and severe dysplasia in 1 patient (17% total dysplasia) compared to mild dysplasia in 13 group B patients, moderate in 1, and severe in 1 patient (50% dysplasia) (RR=3.00; CI 1.01–8.95). Only patients with moderate and severe dysplasia (1 in group A and 2 in B) were treated. (RR=I.20; CI 0.12–12.31) Among untreated patients compliant with follow-up. 1 of 12 in group A with Pap smears in the following year had an abnormal, whereas 7 of 21 in group B had an abnormal smear. (RR=4.00; CI 0.56–28.73) Conclusions This study revealed measurable differences in rates of dysplasia between patients with ASCUS favor reactive/inflammation compared to ASCUS favor HPV/dysplasia. However, high grade lesions were found at a similar rate. Although repeat abnormal cytology may be less common after an ASCUS favor reactive smear. these results suggest that deferment of colposcopy for the adolescent with ASCUS of any type risks delay of necessary therapy.