We report a study under pressure on the field dependence of magnetic s
usceptibility chi(H) and magnetoresistivity rho(H) on single crystals
of the weakly itinerant helimagnet system MnSi. Close to the critical
pressure P-c = 14.8 kbar, the shapes of chi(H) and rho(H) indicate som
e metamagnetic behaviors induced by the external magnetic field.