EN
We study the reflexivity of the automorphism (and the isometry) group of the Banach algebras $L_{∞}(μ)$ for various measures μ. We prove that if μ is a non-atomic σ-finite measure, then the automorphism group (or the isometry group) of $L_{∞}(μ)$ is [algebraically] reflexive if and only if $L_{∞}(μ)$ is *-isomorphic to $L_{∞}[0,1]$. For purely atomic measures, we show that the group of automorphisms (or isometries) of $ℓ_{∞}(Γ)$ is reflexive if and only if Γ has non-measurable cardinal. So, for most "practical" purposes, the automorphism group of $ℓ_{∞}(Γ)$ is reflexive.