This study was undertaken to identify histopathologic risk factors in 100 women with stage IB squamous cell carcinoma of the cervix treated surgically. Histologic factors included maximum depth of stromal invasion, presence of lymph-vascular invasion, mitotic activity, nature of the tumor-stromal borders, plasma cell-lymphocyte stromal response, histologic grade, and metastases to regional lymph nodes. Using a multifactorial analysis, the maximum depth of stromal invasion was found to be the most important prognostic indicator (P less than .0001). The depth of invasion also correlated significantly with the presence of nodal metastases (P less than .0001), lymph-vascular space invasion (P = .0003), and "spreading" versus "pushing" borders (P = .0315). The number of mitoses, grade of tumor, or plasma cell-lymphocyte stromal response did not correlate significantly with depth of stromal invasion. Lymph-vascular involvement, although present in 59% of the patients, did not significantly affect survival. Depth of stromal invasion and lesion diameter were combined to constitute three risk groups: Patients with small size cervical tumors (less than 2 cm), regardless of depth of stromal invasion, as well as patients with intermediate size lesions (2.1 to 3 cm) with stromal invasion less than or equal to 1.5 cm, constituted a low-risk group; the intermediate-risk group was comprised of those patients with cervical lesions between 2.1 and 3 cm in size and deep stromal invasion (greater than 1.5 cm), as well as those patients with large cervical lesions (greater than 3.0 cm) and stromal invasion less than or equal to 1.5 cm.2+ (greater than 3 cm) and deep stromal invasion (greater than 1.5 cm).(ABSTRACT TRUNCATED AT 250 WORDS)