This work establishes local existence and uniqueness as well as blow-up criteria for solutions (u, b)(x, t) of the Magneto-Hydrodynamic equations in Sobolev-Gevrey spacesḢ s a,σ (R 3). More precisely, we prove that there is a time T > 0 such that (u, b) ∈ C([0, T ];Ḣ s a,σ (R 3)) for a > 0, σ ≥ 1 and 1 2 < s < 3 2. If the maximal time interval of existence is finite, 0 ≤ t < T * , then the blow-up inequality C 1 exp{C 2 (T * − t) − 1 3σ } (T * − t) q ≤ (u, b)(t) Ḣs a,σ (R 3) with q = 2(sσ + σ 0) + 1 6σ holds for 0 ≤ t < T * , 1 2 < s < 3 2 , a > 0, σ > 1 (2σ 0 is the integer part of 2σ).