The National Geodetic Survey recently released version 2.6 of the HTDP (Horizontal Time-Dependent Positioning) software for transforming positional coordinates and/or survey observations across time and between reference frames. Users may also apply HTDP to predict the velocities and displacements associated with crustal motion in any of several different reference frames. Version 2.6 expands the list of permissible reference frames to include the International Terrestrial Reference Frame of 2000 (ITRF00). Users may execute HTDP_2.6interactively at http://www.ngs.noaa.gov by clicking their mouse on “geodetic tool kit” and then on “HTDP.”