The upper critical field Hc2 for the fields perpendicular and parallel to Mg and B planes of the magnesium diboride is presented in the temperature range from 5.4 K up to Tc as obtained by comparison of high-field magnetotransport, ac-susceptibility and specific heat measurements. The onset of the finite resistivity yields Hc2, while the end of the resistive transition to the normal state is due to surface effects. Hc2 perpendicular to the planes reveals a conventional temperature dependence with μ0Hc2⊥ab(0) = 3.5 T but the parallel critical field with μ0Hc2||ab(0) = 17 T has a positive curvature at temperatures above 20 K. Consequently, the anisotropy factor Γ = Hc2||ab/Hc2⊥ab is temperature dependent with Γ equal to 4.8 at low temperatures and about 2 near Tc. The angular dependence of the upper critical field of an elliptic form is obtained at several temperatures.