A SAR study has been performed in order to evaluate how much the ester function could be a determinant for the anti-human immunodeficiency virus type-1 activity of pyrryl aryl sulfones (PASs), a potent family of non-nucleoside reverse transcriptase (RT) inhibitors discovered in the last years. Twenty-three new esters were prepared with the aim to enhance the inhibitory potency of 4a and 4c, two PAS agents endowed with good activity (EC50 = 0.14 microM) and deprived of cytotoxicity up to >200 microM. None of test derivatives was as potent as 4a and 4c and lacked of selectivity due to their higher cytotoxicity (compounds 22-25). Antiviral activity correlate with an ester ramified chain.