Abstract. We give explicit examples of pairs of Julia sets of hyperbolic rational maps which are homeomorphic but not quasisymmetrically homeomorphic.Quasiconformal geometry is concerned with properties of metric spaces that are preserved under quasisymmetric homeomorphisms. Recall that a homeomorphism h : X → Y between metric spaces is quasisymmetric if there exists a distortion control function η : [0, ∞) → [0, ∞) which is a homeomorphism and which satisfies |h(x) − h(a)|/|h(x) − h(b)| ≤ η(|x − a|/|x − b|) for every triple of distinct points x, a, b ∈ X. We shall say that X and Y are quasisymmetrically equivalent if there exists such a homeomorphism.A basic -even if still widely open-question is to determine whether two given spaces belong to the same quasisymmetry class, once it is known that they are homeomorphic and share the same qualitative geometric properties. This question arises also in the classification of hyperbolic spaces and word hyperbolic groups in the sense of Gromov [BP, Kle, Haï]. Besides spaces modelled on manifolds, very few examples are understood; see nonetheless [Bou] for examples of inequivalent spaces modelled on the universal Menger curve. Here, we focus our attention on compact metric spaces that arise as Julia sets of rational maps. A rational map is hyperbolic if the closure of the set of forward orbits of all its critical points does not meet its Julia set. We address the question of whether the geometry of the Julia set of a hyperbolic rational map is determined by its topology. More precisely, given two hyperbolic rational maps f and g with homeomorphic Julia sets J f and J g , does there exist a quasisymmetric homeomorphism h :Hyperbolic Julia sets serve our purposes for several reasons. First, it rules out elementary local obstructions. For instance, the Julia set of f (z) = z 2 is the Euclidean unit circle S 1 , while that of g(z) = z 2 + 1/4 is a Jordan curve with a cusp at the unique fixed-point, so they are not quasisymmetrically equivalent. Second, if f is hyperbolic, it is locally invertible near J f , and the inverse branches are uniformly Date: July 2, 2018.