Objective: To evaluate the performance of laboratories accredited by the National Health System that perform cytopathology examination of the uterine cervix after 10 years of participation in external quality monitoring (eQM). Study Design: Seven laboratories were assessed in this study. To assess the concordance of the representation of epithelia and results, 6,536 examinations (3,433 in 2007 and 3,103 in 2017) were reviewed. Statistical analysis was performed using the κ coefficient as well as the χ2 and the Fisher exact test (p < 0.05). Results: All laboratories showed adequate infrastructure and internal quality monitoring. Regarding the representation of the epithelia, the concordance remained excellent (κ between 0.84 and 0.94). In 2007, 26 false-negative results (FN), 157 false-positive results (FP), and 79 delays in clinical conduct (DCC) were identified (κ = 0.80). In 2017, 24 FN, 42 FP, and 38 DCC were identified (κ = 0.90). Five laboratories showed improvement in concordance from 2007 to 2017. We observed significant improvement in cytomorphological criteria of the results: atypical squamous cells of undetermined significance (p < 0.001), atypical squamous cells cannot exclude high-grade squamous intraepithelial lesion (p < 0.016), and low-grade squamous intraepithelial lesion (p < 0.001). We also observed a considerable improvement in the results of cellular abnormalities in glandular epithelium (p < 0.0504). Conclusions: Ten years after the implementation of eQM, improvements in the concordance of results were observed as well as reductions in FN, FP, and DCC in all laboratories monitored.