Non-nucleoside reverse transcriptase inhibitors (NNRTIs) have become very important components in the antiretroviral combination therapies used to treat HIV. Recently, our group identified some 1,3-dihydrobenzimidazol-2-one derivatives and their sulfones as a potent and novel class of NNRTIs. We herein report the synthesis and biological evaluation of the new compounds in which different structural modifications have been introduced in order to investigate their effects on RT inhibition.