Hexagonal zinc oxide (ZnO) nanotubes were synthesized from 0.05 M zinc nitrate hexahydrate [Zn(NO3)2·6H2O] and hexamethylenetetramine (C6H12N4) by a sonochemical method under ambient conditions. White precipitates, obtained after ultrasonic irradiation for 60 min, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). The ZnO crystals had a tubular structure ∼500 nm in length with a hexagonal cross section for both the inner and outer walls. The room temperature PL spectrum of ZnO nanotubes exhibited an ultraviolet (UV) emission peak, a sharp violet peak and a further broad visible band centered at 650 nm.