Quantum chemical ab initio calculations at the complete active space SCF level and with inclusion of correlation effects have been performed for the potential energy surfaces of PH in its X (3) Sigma(-) ground state and its first excited triplet state, A (II)-I-3, colliding with He atoms. The PH distance was fixed at its experimental value (of the A (II)-I-3 state), the PH-He distance and the HePH angle were varied. All three potential energy surfaces [1 (3)A " for PH(X)-He and 1 (3)A’,2 (3)A " for the two components of PH(A)-He] are purely repulsive, except for very shallow van der Waals minima with well depths of about 15-40 cm(-1). The interaction potentials decay approximately exponentially with increasing PH-He distance and show large angular anisotropies. Legendre expansions for the angular dependence of the potential surfaces converge slowly for V(1 (3)A ") and the sum potential 1/2[V(2 (3)A ") + V(1 3A’)], but rapidly for the;corresponding difference potential 1/2[V(2 (3)A ") - V(1 (3)A’)]. Th, present PH(A) -He potentials;have been used in the companion paper by Neitsch et al. [J. Chem. Phys. 106, 7642(1997)], for the calculation of thermal state-to-state rate constants for inelastic PH(A)-He collisions.