A combination of variable-temperature, multinuclear n.m.r. studies (1H, 13C, 103Rh, 1H-{103Rh}, and 13C-{103Rh}) has allowed the ligand (CO/H) migrations in [Rh13(CO)24Hn](5 –n)–(n= 1–4) and [Rh14(CO)25HX](4 –x)–(x= 0 or 1) to be established. In both types of compound, interstitial H migration is found at room temperature with complete randomisation of carbonyls in the Rh14 clusters and partial migration of carbonyls in the Rh13 clusters; in neither case is there evidence for rearrangement of the metal polyhedron. At low temperatures (–90 °C), H migration still occurs in [Rh14(CO)25H]3– but not in [Rh13(CO)24H3]2– and [Rh13(CO)24H2]3– which have the same structural features as found in the solid state with the hydride ligands occupying pseudooctahedral holes in the metal skeleton. All the values of δ(103Rh) for the interstitial rhodium atoms are at significantly higher frequency than the values for the surface rhodium resonances and shift significantly to lower frequency with increasing interstitial hydride content.