The near edge x-ray absorption spectra of CX4 (X = H, F, Cl)have been measured with high resolution at the 1s edges ofcarbon and fluorine, and the 2p edge of chlorine. The absolutephotoabsorption cross section has been determined at theresonances and in the nearby continuum. In accord with previouswork, the antibonding valence peaks of the halides do not showany vibrational structure but sharp Rydberg states are observedat the C 1s edge. We report the first detailed study of theCCl4 Rydberg states. The vibrational frequency of theCF4 Rydberg states is anomalously high, which we attributeto a Fermi resonance. The C 1s line widths were compared totheoretical predictions of ion state line widths and reasonablevalues are found for CH4 and CCl4, but for CF4the measured value is higher than the theoretical value. Thediscrepancy is assigned to mixing of valence band character inthe Rydberg states, which is especially strong in CF4, andto multi-centre autoionization. Finally the integratedoscillator strength below threshold is shown to vary in theorder CF4 > CH4 > CCl4.