The electronic spectrum of GeS has been studied by using ab initio based multireference configuration interaction calculations which include relativistic effective core potentials of Ge and S atoms. Potential-energy curves of 27 Lambda -S states of GeS correlating with two dissociation limits have been computed. Spectroscopic constants of bound states are computed and compared with some of the observed states such as X(1)Sigma (+), a(3)Sigma (+), b(3)Pi, A(1)Pi, and E(1)Sigma (+). The ground state of GeS is composed of two dominant configurations:...sigma (2)pi (4) and ...sigma (2)pi (3)pi* with r(e) = 2.039 Angstrom and omega (e) = 549 cm(-1), which compare well with the observed values. The ground-state dissociation energy of GeS is also estimated. The observed E state is assigned to 2(1)Sigma (+). Effects of the spin-orbit coupling have been explored on 18 Lambda -S states all of which converge with the lowest dissociation limit P-3(g)(Ge) + P-3(g)(S). Potential-energy curves of all 50 Omega states arising from the spinorbit interactions in these Lambda -S states are computed. Transition probabilities of some dipole-allowed transitions are estimated. Transitions such as b(3)Pi (0+)-X(1)Sigma (+)(0+) and b(3)Pi (1)-X(1)Sigma (+)(0+) which are analogous to the Cameron bands of the isovalent CO are investigated. The observed a(3)Sigma (+)(1)-X(1)Sigma (+)(0+) transition of GeS is also studied. Radiative lifetimes of A(1)Pi (1), E(1)Sigma (+)(0+), a(3)Sigma (+)(1), b3 Pi (0+), b(3)Pi (1), and some other components are estimated.