The complexes [Re(η²-Me₂NCH₂CH₂O)(CO)₃(μ-OH)Re(η²-Me₂NCH₂CH₂OH)(CO)₃] (1) and [Re₃(μ₃-OH)(μ-OH)₂(μ-OCH₂CH₂NMe₂H)(CO)₉] (2) have been synthesised and characterised by single-crystal X-ray diffraction analysis. Complex 1 exists as hydrogen-bonded dimers in the solid state and in solution. Proton NMR, ¹H–¹H COSY and NOESY spectroscopic studies showed that the structure of 1 is static in solution, and that only one of the many possible geometric isomers of 1 exists. The hydrogen atom on the ammonio nitrogen of 2 is involved in intramolecular NH⋯O hydrogen-bonding with a bridging OH group. Complexes 1 and 2 were shown to be potent in suspended tumour cell lines in suppressing growth but were more selective in inhibiting the growth of cultures from solid tumours. The compounds [NBuⁿ₄][ReO₄] and [NEt₄]₂[ReBr₃(CO)₃] were also very active against the suspended cell lines and selective against solid tumours. All the compounds tested are inactive against normal cells.