The microscopic pathologic features of early invasive squamous cell cervical carcinoma are used as determinants for the treatment of these lesions. This study is a retrospective review of 180 patients with squamous cell cervical carcinoma with invasion to a depth of 5 mm or less. Invasion of less than or equal to 1 mm, greater than 1 but less than or equal to 3 mm, greater than 3 but less than or equal to 5 mm was noted in 37, 84, and 59 patients, respectively. The median follow-up was 6.5 years. Four (2.2%) patients developed carcinoma in situ of the vagina and four (2.2%) patients progressed to invasive squamous carcinoma. Pelvic lymph node metastases were rare (1%). No patient has died from recurrent disease. Analysis of numerous clinical and pathological variables identified no risk factors for recurrence. Most (54/68) patients with tumor invading beyond 3 mm or with tumor demonstrating vascular invasion were treated by traditional "radical" methods. This limited a meaningful analysis of the risk of conservative treatment. The reliability of using the existing definitions of microinvasive disease for the guidance of treatment remains controversial. Further clarification may be rendered only with prospective clinical-pathologic studies performed by cooperative groups.