The surgical tissues and clinical records of 54 surgically treated patients with microinvasive carcinoma of the cervix were retrospectively analyzed. Utilizing a definition that limited microinvasion to a depth of 3 mm, and excluded lymphatic and blood vascular involvement, the incidence of regional metastases in 37 patients for whom lymph nodes were available for study was 0%. Confluence of microinvasion did not imply a greater potential for metastatic spread or a worse prognosis. Lymphatic and blood vascular permeations were associated with nodal metastasis in one of four lesions which otherwise were microinvasive. Random cervical biopsy alone was inadequate for the diagnosis of microinvasion. Cone biopsy demonstrated an accuracy of 83% in diagnoses, but failed to eliminate intraepithelial or microinvasive carcinoma in 78% of the hysterectomy specimens. It is concluded that microinvasive carcinoma, as defined in this study, can be effectively treated by conservative rather than radical means.