No-overlap and orientation principles for ferromagnetic interactions between organic radicals were derived on the basis of approximately spin-projected UMP4(2) and UCC SD(T)/4-31G computations for several typical radical pairs. Ferromagnetic intermolecular interactions are feasible at T-shape and rhombus conformations in parallel interplane orientations for radical pairs because of no-overlap between pi*-type SOMOs (no kinetic exchange) and nonzero-potential exchange via the SOMO-SOMO through-space contact, whereas antiferromagnetic kinetic exchange interactions are predominant at many other conformations.