The magnetic properties of the two-chain compounds based on perylene (Per) and metal-bis(maleonitriledithiolate) (M(mnt)(2)) with general formula (Per)(2)M(mnt)(2), M = Cu and Ni, either alpha or beta polymorphs, were studied by EPR and static magnetic susceptibility in the range 4-300 K. The EPR spectra of single crystals of the Cu compounds show a relatively narrow line (0.3 and 4 G at room temperature for the alpha and beta phases, respectively) with g values close to those of perylene, consistent with a full charge transfer (Per)(2)(+)[M(mnt)(2)](-) and a diamagnetic organometallic species. The EPR spectra of the Ni compounds show wider (300 and 180 G at room temperature for the alpha and beta phases, respectively) and anisotropic lines with temperature-dependent g values, denoting spin exchange between the electrons on the perylene cations and the Ni(mnt)(2)(-) units. The highly conducting alpha-Cu phase has a magnetic susceptibility due to a small and almost temperature-independent contribution of the perylene conduction electrons that vanishes at the metal to insulator transition at 33 K. The alpha-Ni compound, in addition to a similar Paul-like contribution, has its magnetic susceptibility dominated by a larger term due to the chains of Ni(mnt)(2)(-) spins, also vanishing at the metal to insulator transition (25 K). The magnetic susceptibility of the semiconducting P-phases of the Cu and Ni compounds shows a distinct behavior with a continuous increase of susceptibility upon cooling following a T--alpha law, with alpha similar or equal to 0.8, indicative of disorder. These results are compared with those of the other members of this family of compounds, and for the a-compounds, they are discussed- in terms of the instabilities occurring in the conduction perylene chains (Peierls) and in the Ni(mnt)(2) spin chains (spin-Peierls).