Our investigations were based on the occurrence of cervical smear cell pictures where definitive cytological evaluation regarding malignancy/atypia was impossible due to quality loss for different reasons. In a retrospective cross-sectional study we analysed 216 histologically clarified cervical findings in 245 women whose cytological smears--out of a total of 277,677 smears over a 3-year period (1987-1989)--were placed in group III according to Papanicolaou (suspect malignancy/atypia or undetermined value). This subgroup of group III according to Papanicolaou amounted to 0.088% (on average 82 out of 92,559 smears a year) of the total amount of smears. The histological clarification of suspect or undetermined cytological cell pictures revealed a precancerous or cancerous condition in almost three quarters (72.2%) of the cases. Cervical intraepithelial neoplasia, grade III (CIN III) shows the highest prevalence at 40.3% (carcinoma in situ amounted to 22.2% and high-grade dysplasia 18.0%) and the subgroup "non-malignancy" shows the second highest prevalence at 27.8% (regenerated epithelium--18.5%, benign glandular changes--4.2%, abnormal epithelium--3.7%, others 1.3%). In cases of suspected malignancy/atypia or indeterminate cytological cell picture we strongly emphasize the necessity of clarification of the cervical canal findings by means of curettage when colposcopy of the ectocervix shows no pathological findings. Carcinoma in situ, high-grade dysplasia and regenerated epithelium are the most frequent causes of cytodiagnostic problems in those cases in which the quality of the cell picture is reduced.