Reaction of tris(acetylacetonato)gallium(III) with 1,1,1-tris(5-methoxysalicladiminomethyl)ethane, H3[(5-MeOsal)3 TAME], affords a neutral six-coordinate complex, Ga[5-MeOsal)3 TAME], for which the x-ray crystal structure is reported. The 67Ga and 68Ga complexes of H3[(5-MeOsal)3 TAME] and the bis(salicylaldimine) of triethylenetetramine were prepared and characterized by paper chromatography and electrophoresis. The biodistribution of lipophilic 68Ga[(5-MeOsal)3 TAME] was determined following intravenous injection in rats. Myocardial images obtained by positron emission tomography from three dogs injected with 68Ga[(5-MeOsal)3 TAME] show a correlation between 68Ga uptake and regional myocardial blood flow. Single-pass coronary extraction studies in open-chest dogs indicate that 68Ga[(5-MeOsal)3 TAME] behaves neither as a freely diffusible tracer nor as a microsphere analog.