Patients diagnosed with CIN3 on biopsy without a Pap smear are an inevitable correlate of the extensive utilization of colposcopy as a basic screening test. In a series of 248 CIN3 cases diagnosed on biopsy and notified to the Romagna Cancer Registry between 1986 and 1993, we evaluated the independent association between the Pap smear result and (1) the final histology diagnosis, (2) the first choice treatment, and (3) the appropriateness of hysterectomy. The patients were grouped into the following categories: (1) no smear, ie colposcopy only (n = 40 or 16%), (2) CIN1, CIN2, LGSIL, and minor changes, (3) CIN3 and HGSIL, and (4) carcinoma. In multiple logistic regression analysis, patients without a Pap smear were used as a reference category. Patients with smears reported as CIN1-2/LGSIL or less as well as CIN3/HGSIL had a significantly lower probability of invasive squamous carcinoma (odds ratio = 0.26 for both categories) compared with those not undergoing cytology. The Pap smear result was not a determinant of the first choice treatment. Hysterectomy had a greater probability of being unnecessary if performed in patients with smears reported as showing CIN3/HGSIL (odds ratio = 5.05) or less. In conclusion, this registry-based study demonstrated that the Pap smear had an independent but neglected value in the assessment of cases reported as CIN3 on colposcopy-guided biopsy.