A novel 4-substituted-1,2,3,6-tetrahydrophthalic acid anhydride represented by the structural formula [I]: ##STR1## where R.sup.1 represents a lower alkoxy group, and R.sup.2 and R.sup.3 each represents a lower alkyl group or a lower alkoxy group, said 4-substituted-1,2,3,6-tetrahydrophthalic acid anhydride being liquid. The novel compound is useful as coupling agents, plasticizers, curing agents, etc.