The high-pressure behavior of molybdenum disulfide (MoS 2) has been investigated using an energy dispersive synchrotron X-ray diffraction method in a diamond anvil cell to 38.8 GPa at room temperature. It is found that the c-axis compression ratio is about three times larger than a-axis at pressures below 10 GPa. It gradually decreases with increasing pressure, and reduces to two times above 28.9 GPa. The reduction of c-axis with pressure displayed a discontinuity between 20.5 and 28.9 GPa. This may result from a phase transformation. The experimental pressure–volume data below 20.5 GPa were fitted with the third-order Birch–Murnaghan equation of state, and the bulk modulus was obtained as K 0T=53.4±1 GPa and its pressure derivative as K′ 0T=9.2±0.4.