Abstract. Blow-analytic equivalence is a notion for real analytic function germs, introduced by Tzee-Char Kuo in order to develop real analytic equisingularity theory. In this paper we give complete characterisations of blow-analytic equivalence in the two dimensional case: in terms of the real tree model for the arrangement of real parts of Newton-Puiseux roots and their Puiseux pairs, and in terms of minimal resolutions. These characterisations show that in the two dimensional case the blow-analytic equivalence is a natural analogue of topological equivalence of complex analytic function germs. Moreover, we show that in the two-dimensional case the blow-analytic equivalence can be made cascade, and hence satisfies several geometric properties. It preserves, for instance, the contact orders of real analytic arcs.In the general n-dimensional case, we show that a singular real modification satisfies the arc-lifting property.A classical result of Burau [4] and Zariski [34] shows the embedded topological type of a plane curve singularity (X, 0) ⊂ (C 2 , 0) is determined by the Puiseux pairs of each irreducible component and the intersection numbers of any pairs of distinct components. It can be shown, cf. [30], that the topological type of function germs f : (C 2 , 0) → (C, 0) is completely characterised, also in the non-reduced case f = f In this paper we give a real analytic counterpart of these results and show that the two variable version of blow-analytic equivalence of Kuo is classified by invariants similar to Puiseux pairs, multiplicities of irreducible components, and intersection numbers. Moreover we show several natural geometric properties of this equivalence, answering previously posed questions. In the main result of this paper we a give complete characterisation of blow-analytic equivalence classes of two variable real analytic function germs.Theorem 0.1. Let f : (R 2 , 0) → (R, 0) and g : (R 2 , 0) → (R, 0) be real analytic function germs. Then the following conditions are equivalent:(1) f and g are blow-analytically equivalent.(2) f and g have weakly isomorphic minimal resolution spaces. (3) The real tree models of f and g are isomorphic.Moreover if f and g are blow-analytically equivalent then they are equivalent by a cascadeblow-analytic homeomorphism.1991 Mathematics Subject Classification. Primary: 32S15. Secondary: 14B05.