The purpose of this study was to explore the effects of titanium dioxide (TiO2) on vascular smooth muscle contractility with the use of the rat carotid-artery model. TiO2 powder was implanted on right carotid arteries of five albino rats, the left arteries of which were left intact and served as controls. Fourteen days after placement, bilateral carotid arteries were removed and contraction/relaxation of isolated vessel rings were measured for dose-dependent epinephrine and acetylcholine administrations by a force displacement transducer. The data of each tissue specimen were collected with the use of a computerized system and corresponding software at a sample rate of 1000 kHz, and were expressed as contraction force. Contraction forces of control and TiO2-implanted vessel rings were similar (P > 0.05). TiO2 does not appear to have adverse effects on vascular contractility. (C) 2004 Wiley Periodicals. Inc.