The structures of trimethylindium (Me3In) adducts with the bidentate tertiary amine N,N,N',N'-tetramethyl-4,4'-methylenebis(aniline)[MBDA] and the macrocyclic amines 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane [N-4-aza crown] and 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane [N-6-aza crown] have been determined by single crystal X-ray diffraction. The adducts have the following stoichiometries, Me3In . 2MBDA 1, 2Me(3)In . MBDA 2, 4Me(3)In .N-4-aza crown 3 and 6Me(3)In .N-6-aza crown 4. Compound 1 contains five-coordinate Me3In in a trigonal bipyramidal configuration and displays the longest In-N bond lengths yet reported (2.720(4), 2.865 Angstrom); 2-4 contain four-coordinate Me3In molecules in a tetrahedral configuration. Compounds 1-4 can be used as intermediate adducts in the adduct purification of Me3In for use in the MOVPE (metal organic vapour phase epitaxy) of InP and related III-V semiconductors.The structures of trimethylindium (Me3In) adducts with the bidentate tertiary amine N,N,N',N'-tetramethyl-4,4'-methylenebis(aniline)[MBDA] and the macrocyclic amines 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane [N-4-aza crown] and 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane [N-6-aza crown] have been determined by single crystal X-ray diffraction. The adducts have the following stoichiometries, Me3In . 2MBDA 1, 2Me(3)In . MBDA 2, 4Me(3)In .N-4-aza crown 3 and 6Me(3)In .N-6-aza crown 4. Compound 1 contains five-coordinate Me3In in a trigonal bipyramidal configuration and displays the longest In-N bond lengths yet reported (2.720(4), 2.865 Angstrom); 2-4 contain four-coordinate Me3In molecules in a tetrahedral configuration. Compounds 1-4 can be used as intermediate adducts in the adduct purification of Me3In for use in the MOVPE (metal organic vapour phase epitaxy) of InP and related III-V semiconductors.