An EPR study of two phases of manganese-doped lanthanum gallate (with a first-order structural transition occurring at 430 K) has revealed Gd(3+), Fe(3+), and Mn(4+) centers at room temperature and 438 K. The parameters of spin Hamiltonians are determined for the Gd(3+), Fe(3+), and Mn(4+) rhombohedral centers in the high-temperature phase (with no other centers found here) and for the monoclinic center Gd(3+) in the low-temperature phase. Both in the orthorhombic and in the rhombohedral phase, crystallographic twins (or ferroelastic domains) are observed.