Electrochemical synthesis of poly- and single-crystalline Au wires with diameters ranging down to 25 nm in porous polycarbonate templates is described. These templates have been prepared using heavy-ion irradiation and subsequent transformation of the ion tracks into nanopores by chemical etching. Crystallographic and morphological properties of these nanowires have been investigated by X-ray diffraction, transmission and scanning electron microscopy. The effect of deposition conditions including temperature, electrolyte, voltage signal and diameter on the texture of gold nanowires is investigated and described in detail in this work. In addition, the structural stability of wires is discussed in detail. The wires became morphologically fragile due to Rayleigh instability when annealed at high temperatures. During this process they fragmented into nanospheres at temperatures far below the bulk melting point. Thus a wire with diameter 25 nm decayed already at 300 oC. The electrical resistance of single gold nanowires, embedded in the template, has also been investigated.