For accurate cervical cytology an adequate sample of cells must be obtained from the squamocolumnar junction. In 100 patients conventional smears were compared with smears and membrane filter preparations made using a cytobrush. A satisfactory cell smear was obtained in 39% of patients using the conventional method and in 97% the cytobrush. When membrane filter preparations were used in conjunction with cytobrush smears, adequate cytological samples were obtained from all patients.