Geometries of the gallium arsenide doublet radicals GaAs2, Ga2As, Ga2As3, Ga3As2, GaAs4, and Ga4As were optimized by the B3LYP/6-311+G(2df) method and compared with literature values. For the global minimum, as well as for isomers lying up to 0.2 eV higher, hyperfine coupling constants (HFCC) and electron-spin g-tensors were calculated. For HFCCs the B3LYP/6-311+G(2df) method was used, whereas for g-tensors second-order perturbation calculations with multireference configuration interaction wave functions and a valence triple-zeta basis set with polarization functions (TZVP) were performed. Generally, due to the low s-spin and high p-spin densities, A(iso) values are small, and A(dip)'S large. The g-shifts (Deltag = g - g,) are on the order of 100 000 ppm, caused by large spin-orbit couplings and low excitation energies. For the experimentally known Ga2As3, values calculated for the D-3h structure are (A's in MHz, Deltag's in ppm) A(iso)(Ga-69) = 1325 (1524); A(iso)(As-75) = -23 (65); A(dip)(Ga-65) = 65 (87); A(dip) (As-75) = 36 (0); Deltag- = -73 410 (-82 300); and Deltag(perpendicular to) = 6460 (0), with magnetic parameters derived from the experimental values in parentheses. Mulliken spin densities are shown to be a good measure of Adip values. Vertical excitation energies, as obtained from the g-tensor calculations, are also tabulated.