The cervical cytology in 53 cases with histologically confirmed microinvasive squamous-cell carcinoma of the uterine cervix was studied. The smears were originally correctly diagnosed as showing microinvasion in 42% of the cases and were underinterpreted in 45%. On review, four of the underdiagnosed smears did show features of microinvasion. The depth of invasion did not have much influence on the cellular features. The patients underdiagnosed by cytology showed a tendency to have a smaller surface lesion and to have a history of a prior cervical manipulation within four weeks of the cytologic examination. The mean age of the overdiagnosed cases was distinctly higher than that of other cases. The colposcopic diagnosis correlated well with the cytologic diagnosis; both diagnostic modalities were considered to reflect well the change within the surface epithelium but to be less sensitive in recognizing the subtle changes of early invasion.