The hydrothermal growths of the ZnO nanorods with the densities ranging from 157 to 73 nanorods/ mu m(2) were achieved by diluting the ZnO seed solution. However, the ZnO seed nanocrystals started to agglomerate for the seed solution diluted below 1% of the original nano-crystalline solutions and resulted in the formation of clustered nanorods. With the assistance of a surfactant, Triton X-100, the nanorod density can be further reduced to 4 nanorods/mu m(2). The diameters of the nanorods depended on the concentration of the seed solution and agitation speed of the nanorod growth solution. More diluted seed solution used and less agitation of the growth solution, the larger diameter of the nanorods was obtained. This indicated that the nanorod growth mechanism was controlled by the diffusion of reactants. With sufficient agitation of the growth solution, the nanorod can be uniformly grown with subjects on any arbitrary geometry. We have demonstrated ZnO nanorods growth on both inside and outside of biliary stents as well as on nitinol wires used as metal stents. The effect of nanorod density on the NIH 3T3 and HUVEC cells growth was also investigated in this study and the results suggested nanorod-coating to be a suitable method for controlling cell adhesion and viability on implantable devices. Published by Elsevier B.V.