Herbicidal agents containing a pyrimido[5,4-e]-as-triazine-5,7-(6H,8H)-dione Ia ##STR1## (R.sup.1, R.sup.2 .dbd.H, C.sub.1 -C.sub.6 -alkyl, C.sub.3 -C.sub.6 -cycloalkyl, C.sub.2 -C.sub.8 -alkenyl, phenyl or benzyl, R.sup.3 .dbd.H, halogen, nitro, C.sub.1 -C.sub.8 -alkyl which may carry up to three further substituents, C.sub.2 -C.sub.6 -alkenyl, phenyl-C.sub.2 -C.sub.6 -alkenyl, C.sub.3 -C.sub.6 -cycloalkyl which may carry up to 3 C.sub.1 -C.sub.4 -alkyl substituents, a 5- or 6-membered heterocyclic structure where up to 2 of the ring members are O, S or NR.sup.4 ; --CO--R.sup.4 or --CO--O--R.sup.4 ; phenyl or hetaryl, which may carry up to 3 further substituents; or ZR.sup.6 ; R.sup.4 .dbd.H, C.sub.1 -C.sub.6 -alkyl; Z.dbd.O, S or --N(R.sup.7)--; R.sup.6 .dbd.H, C.sub.1 -C.sub.6 -alkyl, phenyl or benzyl, which may carry up to 3 further substituents; R.sup.7 .dbd.H, C.sub.1 -C.sub.6 -alkyl or R.sup.6 and R.sup.7 together with nitrogen form a 5- or 6-membered ring which may contain O; n=0 or 1) or a salt of Ia with a mineral acid.