A study has been made of the depth profiling of carbon-implanted titanium by AES combined with argon sputtering. Implantation of¹²C⁺ ions is performed at doses of 5 × 10¹⁷, 1 × 10¹⁸ and 1.5 × 10¹⁸ ions/cm² at an energy of 100 keV. Variation of peak-to-peak intensities of carbon KLL AES spectra with sputtering time is considered to correspond to the depth distribution of atomic concentration of carbon atoms. The variation shows a Gaussian distribution predicted by the range theory at the dose of 5 x 10¹⁷ ions/cm², and trapezoidal one at the dose of 1 x 10¹⁸ ions/cm>² or more. XPS studies reveal, however, that the depth distribution of carbon atom concentration is Gaussian at the dose of 1 x 10¹⁸ ions/cm². Observed titanium LMM AES intensity of TiC mostly agrees with the value calculated by a matrix correction of that of titanium without chemical effect. On the other hand, carbon KLL intensity of TiC is about 2.6 times as large as the value calculated from that of glass-like carbon. The results suggest that the change in intensity of carbon KLL AES spectrum according to the chemical bonding states of carbon atoms makes the depth distribution of carbon atoms a trapezoidal shape at high doses. In conclusion, it is said that the depth distribution of carbon atoms is Gaussian as predicted by the range theory even at very high doses over 1 x 10¹⁸ ions/cm². Therefore, the composition depth profiling of titanium implanted with carbon ions at high doses by AES alone is difficult because of the chemical effect of carbon KLL transition.