The quality of cytological services is the very heart of the prevention of cervical pathologies. Indeed, various studies have demonstrated that inadequate sampling, mistakes made in the organisational and management methods of the screening programme, and incorrect diagnoses result in unnecessarily high incidence and mortality rates. The aim of this work is to compare the effectiveness of two different methods, i.e. a conventional smear test and a liquid based ThinPrep (TP) test. Said methods were tested on a sample 453 cases diagnosed as being "Atypical Squamous Cells of Undetermined Significance"/"Atypical Glandular Cells of Undetermined Significance" according to the 1991 Bethesda System. All the women with an "Atypical Squamous Cells of Undetermined Significance "/"Atypical Glandular Cells of Undetermined Significance" cytological diagnosis were called back within 3 months for a ThinPrep test, as part of the Level 2 diagnostic controls of a cervical cancer screening programme. Of the initial diagnoses of "Atypical Squamous Cells of Undetermined Significance"/"Atypical Glandular Cells of Undetermined Significance" with a conventional smear test, 124 cases (27.4%) were classified as being adequate, while 329 (72.6%) were satisfactory, although they did have limited indicators of quality. Upon repetition of the cytology with a ThinPrep test, 322 cases (71.1%) were found to be adequate, 129 (28.4%) "suboptimal" and 2 inadequate (p < 0.0001). The main reasons for insufficient results in conventional smear tests are: bad preservation (40.2%), the presence of granulocytes (36.4%), intense phlogosis (12.1%) and erythrocytes (5.5%). In liquid based smear tests, the main indicator of quality is the absence of endocervical glandular cells (56.7%). As for the cytological diagnosis, the use of ThinPrep supplied the following results: of the 453 cases diagnosed initially as being "Atypical Squamous Cells of Undetermined Significance"/"Atypical Glandular Cells of Undetermined Significance", 371 (84.1%) were negative, 54 (11.9%) "Atypical Squamous Cells of Undetermined Significance "/"Atypical Glandular Cells of Undetermined Significance" and 18 (4%) L-SIL (p < 0.0001). Histological follow-up of the 18 cases with L-SIL confirmed the presence of a dysplastic lesion in 8 out of 12 cases (66.7%); in 4 cases there was no consistency between the cytological and histological diagnoses, and in 6 patients no biopsy had been taken. The preliminary experience of this study, although indeed carried out on a limited number of cases, appears to show that suitable training for the collection of samples in a liquid solution could improve the adequacy of the sample and thus the precision of the cytological diagnosis.