Abstract.Let G be a connected, simply connected exponential solvable Lie group with Lie algebra 0. The Kirillov mapping n: g*/Ad*(G) -» G gives a natural parametrization of G by co-adjoint orbits and is known to be continuous. In this paper a finite partition of fl*/Ad*(G) is defined by means of an explicit construction which gives the partition a natural total ordering, such that the minimal element is open and dense. Given rr 6 G, elements in the enveloping algebra of gc axe constructed whose images under n are scalar and give crucial information about the associated orbit. This information is then used to show that the restriction of rj to each element of the above-mentioned partition is a homeomorphism.