Three hundred forty-five patients with invasive carcinoma of the uterine cervix, Stages Ib (211 patients) and II (134 patients), underwent radical hysterectomy and pelvic lymphadenectomy. The influence of histologic factors including histologic subtype, maximum depth of cervical stromal invasion, degree of stromal invasion, longitudinal tumor diameter, lymph-vascular space invasion, corpus invasion, parametrial invasion, vaginal invasion, and pelvic lymph node (PLN) metastases on survival were examined by multivariate analysis. Univariate analysis revealed that all the variables except corpus invasion and vaginal invasion were significant in survival (P less than 0.05). Among these variables, however, PLN metastases, histologic subtype, and longitudinal tumor diameter were identified as independent and significant prognostic factors by multivariate analysis using Cox regression models. The prognostic index (PI), defined by the model (an indicator of the patient's place in the prognostic spectrum), was able to divide the patients into three prognostic groups. The key factors in the definition of these groups were (1) squamous cell carcinoma, small tumor diameter, and no PLN metastases for the good prognostic group and (2) PLN metastasis in two or more node groups, adenocarcinoma with one positive PLN group, or squamous cell carcinoma with one PLN group and large diameter for the poor prognostic group. These prognostic findings could predict the prognosis more precisely than that of clinical staging.