The electron ionization mass spectrometric behaviour of a series of diethylindium complexes with imino ligands derived from piperidine, pyrrolidine, azetidine, methylaziridine and dicyclopropylamine were investigated. These data have been compared with those from mass-analysed ion kinetic energy spectrometry. Fragmentation patterns of the complexes in question give information relevant to their gas-phase behaviour as precursors for III-V semiconducting materials via metal-organic chemical vapour deposition. A comparison with analogous derivatives of dimethylindium is also discussed. # 1998 John