The upper critical field H c2 in superconductivity was investigated for CePt 3 Si and CeIrSi 3 without inversion symmetry in the tetragonal structure. A significant anisotropy of H c2 between H ∥[0 0 1] and H ∥[1 0 0] was not observed in CePt 3 Si even at 0.6 GPa as well as ambient pressure, where the Neel temperature with T N = 2.3 K at ambient pressure becomes zero at 0.6 GPa. The similar result was observed at 1.95 GPa in CeIrSi 3 , where antiferromagnetism and superconductivity coexist, while a large anisotropy of H c2 in CeIrSi 3 was observed with increasing pressure: H c2 (0) = 300-40 kOe for H ∥[0 0 1] and H c2 (0) = 95 kOe for H ∥[1 1 0] at 2.65 GPa, which is higher than the critical pressure P c = 2.25 GPa. A large value of H c2 for H ∥[0 0 1] in CeIrSi 3 might become an experimental evidence of the spin-triplet superconductivity in the non-centrosymmetric structure. It is also remarkable that CeIrSi 3 is a strong coupling superconductor and the electronic specific heat coefficient is approximate...