The diagnoses of 1,000 pairs of conventional Papanicolaou (Pap) smears and ThinPrep® preparations were compared. Cervical cells were collected using an Ayre spatula and endocervical brush. The conventional smear was made first, the collection devices were rinsed into PreservCyt® solution, and the slides were prepared using the ThinPrep® Processor. The diagnoses of the paired smears agreed in 988 of the 1,000 cases (98.8%), including 949 negatives, 28 atypicals, 9 low grade squamous intraepithelial lesions (LGSIL), and 2 high grade squamous intraepithelial lesions (HGSIL). Five cases where LGSIL or HGSIL was found on the ThinPrep® slide were negative or atypical on the conventional smear. No conventional smear abnormalities were missed on the ThinPrep® slide. Although not statistically significant, this difference indicates that the ThinPrep® method gives a better diagnosis of abnormalities than the conventional method. The ThinPrep® method was acceptable to participating physicians and ThinPreps® were easier and faster to screen than conventional smears. Diagn Cytopathol 1994; 11:33–37. © 1994 Wiley-Liss, Inc.