Oxidation states of Ti in TS-1 samples prepared by using tetrabutylorthotitanate under various conditions were measured using XPS. Most of the Ti 2p(3/2) spectra comprised of two kinds of core spectra having binding energies of 460.0 +/- 0.2 and 457.8 +/- 0.2 eV, which were due to framework and extraframework Ti4+, respectively. The existence of the extraframework Ti4+ was also ascertained using X-ray diffraction (XRD) and DRUV-Vis. From area intensities of the Ti 2p(3/2) spectra and Si 2p spectrum, x(f) of framework Ti and x(ex) of extraframework Ti were determined and compared with x(g) of precursor gel given by the moles of starting materials used, where the x(f), and x(g) represented the atomic ratio of Ti/(Ti + Si). In TS-1 sample (Y.TS-1) series, prepared using vacuum distilled tetrabutylorthotitanate and 2-propanol, low reaction temperature of 273 K, and an ultrasonic wave vibrator at the aging stage of the precursor gel, a linear relationship between x(f) and x(g) and at x(g) > 0.04 a plateau of x(f) = 0.03 were observed, and good correlations between the relative intensity of XRD peak due to TiO2 and x(g) and between x(ex) and x(g) were established in the range of 0.017 less than or equal to x(g) < 0.10. For other prepared samples, it was, however, difficult to find such regularities. From these results, it was concluded that pure TS-1 samples without extraframework TiO2 were obtained only in x(f) less than or equal to 0.013 and the use of ultrasonic wave vibrator was very effective to facilitate the dispersion of Ti4+ in the precursor gel.