Boron modified nanocrystalline anatase titania powders with boron contents varying from 0.5 to 6.2 wt % were synthesized by a chemical vapor synthesis process. High temperature x-ray diffraction studies revealed that the anatase powders containing more boron were more stable at higher temperatures. When present in small quantities (about 0.5 wt % or less), boron went into the structure of titania and lowered the direct band gap to 3.41 eV. On the other hand, higher boron contents resulted in smaller anatase crystallite sizes and partially offset the redshift. However, the excess boron formed boron oxide which probably coated the surface of the nanoparticles/crystallites resulting in improved high temperature stability of the anatase phase. © 2009 American Institute of Physics.