This study aimed to screen for anal cancer and to determine its cytomorphology using liquid-based cytology (LBC) with specimens preserved in 95% ethyl alcohol. Anal swabs were collected for cytological examination from 177 adult, HIV-infected patients. After collection, sample slides were reviewed and classified according to their cytomorphology using the modified Bethesda 2001 system. An abnormal anal Pap smear was found in 26.0% of the patients. The diagnoses were: 66.7% negative for intraepithelial lesions (NIL), 14.1% with atypical squamous cells of undetermined significance (ASC-US), 10.7% (19) with low-grade squamous intraepithelial lesions (LSIL), and 1.13% with high-grade squamous intraepithelial lesions (HSIL). The cytological evaluation was an unsatisfactory result only with 6.67%. The present modified LBC using 95% ethyl alcohol as the preservative could thus be used for anal cancer screening. The number of SILs in Thai HIV-infected patients is lower than that in Western countries. We found anal cytology a satisfactory tool for early screening and detection of anal dysplasia commonly found in high-risk, HIV-infected patients.