Abstract. We prove the "End Curve Theorem," which states that a normal surface singularity (X, o) with rational homology sphere link is a splice quotient singularity if and only if it has an end curve function for each leaf of a good resolution tree.An "end curve function" is an analytic function (X, o) → (C, 0) whose zero set intersects in the knot given by a meridian curve of the exceptional curve corresponding to the given leaf.A "splice quotient singularity" (X, o) is described by giving an explicit set of equations describing its universal abelian cover as a complete intersection in C t , where t is the number of leaves in the resolution graph for (X, o), together with an explicit description of the covering transformation group.Among the immediate consequences of the End Curve Theorem are the previously known results: (X, o) is a splice quotient if it is weighted homogeneous (Neumann 1981), or rational or minimally elliptic (Okuma 2005).Keywords. Surface singularity, splice quotient singularity, rational homology sphere, complete intersection singularity, abelian cover, numerical semigroup, monomial curve, linking pairing We consider normal surface singularities whose links are rational homology spheres (QHS for short). The QHS condition is equivalent to the condition that the resolution graph of a minimal good resolution be a rational tree, i.e., is a tree and all exceptional curves are genus zero.Among singularities with QHS links, splice quotient singularities are a broad generalization of weighted homogeneous singularities. We recall their definition briefly here and in more detail in Section 1. Full details can be found in [20].Recall first that the topology of a normal complex surface singularity is determined by and determines the minimal resolution graph . Let t be the number of leaves of . For i = 1, . . . , t, we associate the coordinate function x i of C t to the i-th leaf. This leads to a natural action of the "discriminant group" D = H 1 ( ) by diagonal matrices on C t (see Section 1).