We have investigated novel bifunctional chelate alternatives to the aminocarboxylate macrocycles NOTA (N3O3) or DOTA (N4O4) for application of radioisotopes of Ga to diagnostic nuclear medicine and have found that the linear N4O2 chelate H(2)dedpa coordinates Ga-67 quantitatively to form [Ga-67(dedpa)](+) after 10 min at RT. Concentration-dependent coordination to H(2)dedpa of either Ga-68 or Ga-67 showed quantitative conversion to the desired products with ligand concentrations as low as 10(-7) M. With Ga-68, specific activities as high as 9.8 mCi nmol(-1) were obtained without purification. In a 2 h competition experiment against human apo-transferrin, [Ga-67(dedpa)](+) showed no decomposition. Two bifunctional versions of H(2)dedpa are also described, and these both coordinate to Ga-67 at RT within 10 min. Complete syntheses, characterizations, labeling studies, and biodistribution profiles of the Ga-67 complexes are presented for the new platform chelates. The stability of these platform chelates is higher than that of DOTA.