MINOS is a long-baseline neutrino oscillation experiment with two detectors 734 km apart exposed to the Fermilab NuMI neutrino beam. By comparing the energy spectrum and beam composition at the two sites neutrino oscillations at L/E~500 km/GeV can be measured with precision. We present measurements of the atmospheric mass splitting and mixing angle theta-23 for both neutrinos and antineutrinos using observations of charged current neutrino and antineutrino disappearance. The neutrino measurements are based on more than twice the data used in previous publications and the antineutrino measurements are based on a dedicated antineutrino beam run. This is the first precision measurement of antineutrino atmospheric oscillations using a pure sample of muon antineutrinos.