A study was conducted to determine if invasive cervical cancer diagnosed shortly after negative cytologic test results represents a demographically or epidemiologically distinct subgroup of these tumors. A total of 200 patients with invasive squamous cervical cancer and matched, neighborhood control subjects were interviewed. Cytology reports for smears taken 5 years before diagnosis were obtained, and reportedly negative smears were solicited and reevaluated. Thirty-three patients (group 1) had had one or more negative smears within 5 years and no previous abnormal cytologic results. At diagnosis cancers in group 1 had progressed further than those of patients with nondiagnostic positive smears (group 2, n = 43) but not as far as those of patients with no cytologic tests done within 5 years (group 3, n = 96). Age and social class were the same in groups 1 and 2, but both groups were younger and better educated than group 3. Otherwise group 1 did not differ from the other groups and the same risk factors prevailed roughly equally in all three groups. Therefore cervical tumors diagnosed soon after negative cytologic test results do not appear to differ etiologically from other squamous carcinomas at this site, and the failure of screening to detect these tumors is probably due to rapid progression through the preinvasive stages and/or failure to shed cancer cells in quantities sufficient for detection by routine cytologic screening.