Here, non-spin-polarized electronic structures and Fermi surface properties of RX 2Al 20 (R = La, Ce, Yb, Th, U; X = Ti, V, Cr, Mn) intermetallic compounds were calculated using the full potential all-electron local orbital (FPLO) approach in the framework of the local density approximation (LDA). Trends of the magnetism are discussed in terms of the characteristics of X- 3d bands with a quantitative analysis of the relationship between band electron filling and crystal electric field splitting. Since coordination icosahedra of X-atoms have small trigonal distortion, crystal electric field splits the fivefold degenerate X- 3d state into low-energy singlet and two higher-energy doublets e g. In RTi 2Al 20 and RV 2Al 20 the population of the related 3d sub-band is not sufficient to cause energetically favorable spin polarization, whereas magnetic instabilities develop in the RCr 2Al 20 series. Finally, a manifestation of strong repulsive interactions between itinerant Mn-d electrons become most pronounced in ferromagnetic UMn 2Al 20. The influence of non-magnetic R-f states on magnetic and thermodynamic properties is discussed with special emphasis on the role of the f–p and f–d hybridization. For LaTi 2Al 20 and LaV 2Al 20 the calculated quantum oscillation frequencies are in accord with experimental reports