Abstract: 2,4-pyrimidinedione derivatives of formula (I) having high antiviral activity against wild-type and mutant HIV-1 and low toxicity are useful for treating AIDS (I) wherein: R1 is a C6-10 aryl or C3-10 heteroaryl group optionally having one or more substituents selected from the group consisting of halogen, C1-6 alkyl, C1-6 alkyl substituted with one or more halogen atoms, C3-4 cycloalkyl, cyano, nitro, hydroxy, thiohydroxy, azido, C1-6 alkoxy, oximino, C1-3 alkyloximino, O—(C1-6 alkyl)-substituted oximino, C—1-6 alkylcarbonyl, C3-6 cycloalkylcarbonyl, hydroxymethyl, azidomethlyl, C1-6 alkoxymethyl, C1-6 acyloxynethyl, carbamoyloxymethyl, anminomethyl, N—(C1-3 alkyl)aminomethyl, N,N-di(C1-3 alkyl)aminomethyl, carboxy, C1-6 alkoxycarbonyl, aziridine, amino, hydroxyethylamino, cyclopropylamino, C1-6 alkylamino, di(C1-6 alkyl)amino, trifluoroacetamido, C1-6 acylamido, carbamoyl, hydroxyethylcarbamoyl, cyclopropylcarbamoyl, C1-6 alkylcarbamoyl, di(C1-6 alkyl)carbamoyl, aminocarbamoyl, dimethylamin