The compounds CaFe 2 P 2 , SrFe 2 P 2 and BaFe 2 P 2 crystallize in the ThCr 2 Si 2 structure which is a ternary variant of the BaAl 4 structure. In order to investigate the bonding properties, band-structure calculations using the full-potential linearized augmented plane wave (FLAPW) method have been performed. For the three compounds densities of states (DOS), local partial DOS and electron densities have been calculated. Compared to CaNi 2 P 2 with a P-P distance of 2.30 , a value very close to that for a P P single bond, this distance is 2.71 for CaFe 2 P 2 . While in the latter compound one still observes pronounced P P(s s and p p) σ-bonds, this is not the case, apart from very weak p p interactions, for SrFe 2 P 2 and BaFe 2 P 2 (P P distances: 3.43 and 3.84 , respectively). Despite their different c/a ratios the Sr and Ba compounds show fairly similar bonding properties, in particular as far as the Fe Fe and Fe P interactions are concerned. In BaFe 2 P 2 , however, non-negligible interactions of the semicore [Ba(5p)l states with the P(3s) states are found.