The reaction of 2-acetylpyridine 4N-dimethylthiosemicarbazone (HL) with GaCl(3) in absolute ethanol in 1:1 molar ratio yielded the complex [GaL(2)][GaCl(4)]. The crystal structure of the gallium(III) complex has been determined by X-ray diffraction methods. Infrared, electronic, ESI mass and (1)H, (13)C, (15)N and (71)Ga NMR spectra, as well as the thermal behaviour are reported. The cytotoxicity assay in several human cancer cell lines (SW480, SK-BR-3 and 41M) suggests that the gallium(III) complex might be endowed with promising antitumour properties. In vitro cytotoxic activity exceeds that of all other tested gallium(III) complexes and is slightly higher than that of HL.