A study is reported on the relation between orbital ordering and the magnetic structure of an LaMnO3 crystal. The dependence of the exchange parameters on the orbital-structure angle Φ has been determined. Inclusion into the spin Hamiltonian of isotropic exchange interaction and single-ion anisotropy, which depends on the angle Φ and rotational distortions, results in a four-sublattice structure (A X , F Y , G Z ), with the sublattice magnetic moments oriented close to the long axis of the orthorhombic cell in the basal plane of the crystal