A process for the preparation of a spiroheterocyclic pyrrolidine dione compound of formula: wherein X, Y and Z independently of each other are hydrogen, C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 haloalkyl, C 1-4 alkoxy, C 1-4 haloalkoxy, halogen, cyano, C 2-6 alkenyl, C 2-6 alkynyl, phenyl, or phenyl substituted by C 1-4 alkyl, C 1-4 haloalkyl, halogen or cyano; m and n, independently of each other, are 0, 1, 2 or 3 and m+n is 0, 1, 2 or 3; A is hydrogen, C 1-6 alkyl, C 1-6 haloalkyl, C 3-6 cycloalkyl, C 3-6 cycloalkyl(C 1-4)alkyl, C 2-6 alkenyl, C 2-6 haloalkenyl, C 3-6 alkynyl, C 1-4 alkoxy(C 1-4)alkyl, benzyl, phenyl or phenyl substituted by C 1-4 alkyl, C 1-4 haloalkyl, C 1-4 alkoxy, C 1-4 haloalkoxy, halogen or cyano; and W is a group selected from W 1 to W 15: wherein R is hydrogen, C 1-6 alkyl, C 1-6 haloalkyl, C 1-6 cyanoalkyl, C 2-6 alkenyl, C 2-6 haloalkenyl, C 3-6 alkynyl, benzyl, C 1-4 alkoxy(C 1-4)alkyl or C 1-4 alkoxy(C 1-4)alkoxy(C 1-4)alkyl; R q is R; and p is 0,1 or 2; which process comprises (a) treating a compound of the formula or a salt thereof with a suitable base in an appropriate solvent (or diluent) wherein X, Y, Z, m, n, A, and W have the meanings given in the formula above and Q 1 is phenyl or phenyl substituted by one or more substituents selected from the group consisting of C 1-4 alkyl, C 1-4 haloalkyl, C 1-4 alkoxy, halogen, and nitro; and Q 2 is hydrogen; (b) optionally a compound of formula is included in step (a), wherein Q 3 is hydrogen, halogen, C 1-6 alkyl or C 1-6 alkoxy, L is O or N(C 1-6 alkyl) and Q 4 is C 1-6 alkyl, provided the solvent (or diluent), and if necessary the compound of formula, is selected to activate the -NQ 1 Q 2 group to become a leaving group. X, Y and Z independently of each other are hydrogen, C 1-4 alkyl, C 3-6 cycloalkyl, C 1-4 haloalkyl, C 1-4 alkoxy, C 1-4 haloalkoxy, halogen, cyano, C 2-6 alkenyl, C 2-6 alkynyl, phenyl, or phenyl substituted by C 1-4 alkyl, C 1-4 haloalkyl, halogen or cyano; m and n, independently of each other, are 0, 1, 2 or 3 and m+n is 0, 1, 2 or 3; A is hydrogen, C 1-6 alkyl, C 1-6 haloalkyl, C 3-6 cycloalkyl, C 3-6 cycloalkyl(C 1-4)alkyl, C 2-6 alkenyl, C 2-6 haloalkenyl, C 3-6 alkynyl, C 1-4 alkoxy(C 1-4)alkyl, benzyl, phenyl or phenyl substituted by C 1-4 alkyl, C 1-4 haloalkyl, C 1-4 alkoxy, C 1-4 haloalkoxy, halogen or cyano; and W is a group selected from W 1 to W 15: wherein R is hydrogen, C 1-6 alkyl, C 1-6 haloalkyl, C 1-6 cyanoalkyl, C 2-6 alkenyl, C 2-6 haloalkenyl, C 3-6 alkynyl, benzyl, C 1-4 alkoxy(C 1-4)alkyl or C 1-4 alkoxy(C 1-4)alkoxy(C 1-4)alkyl; R q is R; and p is 0,1 or 2; wherein R is hydrogen, C 1-6 alkyl, C 1-6 haloalkyl, C 1-6 cyanoalkyl, C 2-6 alkenyl, C 2-6 haloalkenyl, C 3-6 alkynyl, benzyl, C 1-4 alkoxy(C 1-4)alkyl or C 1-4 alkoxy(C 1-4)alkoxy(C 1-4)alkyl; R q is R; and p is 0,1 or 2; which process comprises (a) treating a compound of the formula or a salt thereof with a suitable base in an appropriate solvent (or diluent) wherein X, Y, Z, m, n, A, and W have the meanings given in the formula above and Q 1 is phenyl or phenyl substituted by one or more substituents selected from the group consisting of C 1-4 alkyl, C 1-4 haloalkyl, C 1-4 alkoxy, halogen, and nitro; and Q 2 is hydrogen; (a) treating a compound of the formula or a salt thereof with a suitable base in an appropriate solvent (or diluent) (b) optionally a compound of formula is included in step (a), wherein Q 3 is hydrogen, halogen, C 1-6 alkyl or C 1-6 alkoxy, L is O or N(C 1-6 alkyl) and Q 4 is C 1-6 alkyl, provided the solvent (or diluent), and if necessary the compound of formula, is selected to activate the -NQ 1 Q 2 group to become a leaving group.