The regulation of a decentralized large-scale linear system which consists of N subsystems S1, S2,…,SN interconnected with a subsystem S0 is investigated. Since in the state-space description the matrix describing the dynamics of this decentralized large-scale system consists of block elements depicting an arrow structure, the system is called a block arrow structure (BAS) decentralized large-scale system and its regulation problem is called a BAS-decentralized large-scale linear regulator problem. In this paper, the time-invariant BAS-decentralized large-scale linear regulator problem is mathematically formulated and a solution to this problem is given by developing a suboptimal linear state feedback controller with the features of (a) partial decentralization (utilizing the interconnections), (b) parallel implementation, and (c) structure flexibility so that the addition and/or deletion of any subsystems within the BAS model specifications does not require the solution of the problem from the beginning ...