Gold nanotubes of small particle sizes down to 5 nm and high aspect ratios were synthesized in ion track etched polycarbonate: following a rational reaction design. 4-(Dimethylamino)pyridine (DMAP) was employed to adjust the electroless deposition by interfering with the autocatalytically active gold surface. Modification of the pH value and DMAP concentration led to a wide range of products which were characterized by SEM, TEM, and EDS. Filigree nanotubes of 10-15 nm wall thickness and 5.0 +/- 2.1 nm grain size were obtained as well as robust and free-standing structures proving homogeneous deposition along the whole template length of 30 mu m. Template-supported gold nanotubes were applied in the UV-vis monitored reduction of 4-nitrophenol by sodium borohydride under pseudo-first-order conditions. They proved to be a reliable microfluidic system of excellent catalytic activity coming up with an apparent rate constant of 1.3 x 10(-2) s(-1). Despite a high flow rate, the reaction showed 99% conversion after a distance of just 60 mu m.