Tensile specimens of α/β brass with the composition of Zn-56.9Cu-3.5Pb (wt-%) were deformed to failure at constant initial strain rates ε̇ of 1 x 10-4 and 1 x 10-2 s-1 in the temperature range of 297-973 K. Unlike the superplastic behaviour of α/β brass, this material was found to exhibit much lower ductility with the minimum values being 11.2 and 16-2% around 873 K at ε̇=1 x 10-4 s-1 and 1 x 10-2 s-1 respectively. This behaviour is attributed to the liquid metal embrittlement owing to the presence of lead in this material. As biased by the embrittling effect, rather than thermally activated deformation process, the evaluation of ductility δ and strain rate sensitivity index m as a function of temperature suggests an anomalous relationship between δ and m. © 2006 Institute of Materials, Minerals and Mining.