  The pressure effect on the superconducting transition temperature of MgB2 has
been determined using gas pressure up to 1 GPa. The transition temperature Tc
was found to decrease linearly at a constant rate over the whole pressure
range. The recently observed dramatic decrease of dTc/dp at the 40 K freezing
pressure (0.5 GPa) cannot be confirmed. The pressure coefficient was also found
to be independent of the hydrostatic or nonhydrostatic He environment. The
differences in recently reported values of dTc/dp may be attributed to
variations in the sample conditions, e.g. stoichiometry.
