Benzodiazepine derivative of formula (I), and pharmaceutically acceptable salts thereof, are found to be active against RSV Formula (I) Wherein: —R1 represents C1-6 alkyl, aryl or heteroaryl; —R2 represents hydrogen or C1-6 alkyl; -each R3 is the same or different and represents halogen, hydroxy, C1-6 alkyl, C1-6 alkoxy, C1-6 alkylthio C1-6 haloalkyl, C1-6 haloalkoxy, amino, mono(C1-6 alkyl)amino, di(C1-6 alkyl)amino, nitro, cyano, —CO2R′, CONR′R″, —NH—CO—R′, —S(O)R′, —S(O)2R′, —NH—S(O)2R′, —S(O)NR′R″ or —S(O)2NR′R″ wherein each R′ and R″ is the same or different and represents hydrogen or C1-6 alkyl; -n is from 0 to 3; R4 represents hydrogen or C1-6 alkyl; —R6 represents C1-6 alkyl, aryl, heteroaryl, carbocyclyl, heterocyclyl, aryl-(C1-6 alkyl)-, heteroaryl-(C1-6 alkyl)-, carbocyclyl-(C1-6 alkyl)-, heterocyclyl-(C1-6 alkyl)-, aryl-C(O)—C(O)—, heteroaryl-C(O)—C(O)—, carbocyclyl-C(O)—C(O)—, heterocyclyl-C(O)—C(O)— or, —XR6; —X represents —CO—, —S(O)— or —S(0)2—; and —R6 represents C1-6 alkyl, hydroxy, C1-6 alkoxy, C1-6 alkylthio, aryl, heteroaryl, carbocyclyl, heterocyclyl, aryl-(C1-6 alkyl)-, heteroaryl-(C1-6 alkyl)-, carbocyclyl-(C1-6 alkyl)-, heterocyclyl-(C1-6 alkyl)-, aryl-(C1-6 hydroxyalkyl)-, heteroaryl-(C1-6 hydroxyalkyl)-, carbocyclyl-(C1-6 hydroxyalkyl)-, heterocyclyl-(C1-6 hydroxyalkyl)-, aryl-(C1-6 alkyl)-O—, heteroaryl-(C1-6 alkyl)-O—, carbocyclyl-(C1-6 alkyl)-O—, heterocyclyl-(C1-6 alkyl)-O— or —NR′R″ wherein each R′ and R″ is the same or different and represents hydrogen, C1-6 alkyl, carbocyclyl, heterocyclyl, aryl, heteroaryl, aryl-(C1-6 alkyl)-, heteroaryl-(C1-6 alkyl)-, carbocyclyl-(C1-6 alkyl)- or heterocyclyl-(C1-6 alkyl)-.