Owing to the high X-ray absorption, Bi2S3 nanocrystals are widely used as CT contrast agents. Here, we prepared uniform Bi2S3 nanorods via a hot injection method using bismuth (III) chloride, sulfur and oleyl amine. The resulting nanocrystals were coated with tetraethylorthosilicate (TEOS) and 2-[methoxy(polyethyleneoxy)propyl]yrimethoxysilane (PEG-silane) for the biological utility. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the Bi2S3 nanorods had an orthorhombic structure with the length of 14 nm and the diameter of 7 nm, respectively. Composite nanoparticles (0.0226 M) gave a CT number at 550 (HU), which was higher than that of the commercial available iobitridol CT contrast agent. Furthermore, cell experiments revealed that Bi2S3 composite nanoparticles had a low cytotoxicity with a concentration up to 0.01 M of Bi for 24 h. (c) 2013 Elsevier Ltd. All rights reserved.