Lattice dynamical calculations of pyrite-type MnS 2, MnSe 2, FeS 2, RuS 2, RuSe 2, PtP 2 and PtAs 2 have been performed using various potential models (short-range, rigid-ion, polarizable-ion). The main results are that: (i) the rigid-ion metal model is most appropriate; (ii) the force constants, vibrational modes, potential energy distributions, etc. differ much more than is usually observed for isostructural series; (iii) the lattice potential is dominated by intraionic X-X (0.9–2.05 N cm −1) and interionic M-X (0.3–1.3 N cm −1) short-range force-constants as well as by Coulomb forces with more or less contributions of interionic repulsive M···M (0.0–0.9 N cm −1) and X 2···X 2(0.0–0.3 N cm −1) forces, especially in the case of d 6 metal ions; (iv) the effective dynamical charges are relatively large (0.7–1.0 e) irrespective of the more (FeS 2), or less (MnS 2), covalent parts of the cohesive energy, and (v) the strengths of the intraionic X-X bonds (bond order 0.4− ∼ 1) strongly decrease of going from d 5-high spin to d 6-low spin metal ions. The eigenvectors and potential energy distributions of the zone-centre phonon modes of the pyrite-type compounds under discussion as well as bonding features of these compounds as far as derivable from lattice dynamics are discussed.